normalize.py now strips before filing:
- <system-reminder>, <command-message>, <command-name> tags
- <task-notification>, <user-prompt-submit-hook>, <hook_output> tags
- Hook status messages (CURRENT TIME, Checking verified facts, etc.)
- Claude Code UI chrome (ctrl+o to expand, progress bars, etc.)
- Collapsed runs of blank lines

This noise was going straight into drawers, wasting storage space
and polluting search results. strip_noise() runs on all normalized
output regardless of input format (JSONL, JSON, plain text).

689/689 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

The closet architecture was always part of MemPalace's design but
never shipped in the public codebase. This adds it.

Palace now has TWO collections:
- mempalace_drawers — full verbatim content (unchanged)
- mempalace_closets — compact AAAK-style index entries

How it works:
- When mining, each file gets a closet alongside its drawers
- Closet contains extracted topics, entities, quotes as pointers
- Closets pack up to 1500 chars, topics never split mid-entry
- Search hits closets first (fast, small), then hydrates the
  full drawer content for matching files
- Falls back to direct drawer search if no closets exist yet

Files changed:
- palace.py: get_closets_collection(), build_closet_text(),
  upsert_closet(), CLOSET_CHAR_LIMIT
- miner.py: process_file() now creates closets after drawers
- searcher.py: search_memories() tries closet-first search,
  hydrates drawers, falls back to direct search

Backwards compatible — existing palaces without closets continue
to work via the fallback path. Closets are created on next mine.

689/689 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

- upsert_closet replaced by upsert_closet_lines: checks each topic
  line individually against CLOSET_CHAR_LIMIT. If adding one line
  WHOLE would exceed the limit, starts a new closet. Never splits
  mid-topic.
- build_closet_lines returns a list of atomic lines (not joined text)
- Richer extraction: section headers, more action verbs, up to 3
  quotes, up to 12 topics per file
- Each line is complete: topic|entities|→drawer_refs

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Cherry-picked the docs portion of 67e4ac6 to accompany the closet
feature. Test coverage for closets is omnibus with tests for entity
metadata and BM25 (see PR targeting those features) and will land
together in a follow-up.

Co-Authored-By: MSL <[email protected]>

Three features that close the gap between the architecture docs
and the actual codebase:

1. Entity metadata on drawers and closets
   - _extract_entities_for_metadata() pulls names from known_entities.json
     + proper nouns appearing 2+ times
   - Stamped as "entities" field in ChromaDB metadata
   - Enables filterable search by person/project name

2. Day-based diary ingest (diary_ingest.py)
   - ONE drawer per day, upserted as the day grows
   - Closets pack topics atomically, never split mid-topic
   - Tracks entry count in state file, only processes new entries
   - Usage: python -m mempalace.diary_ingest --dir ~/summaries

3. BM25 hybrid search in searcher.py
   - _bm25_score() keyword matching complements vector similarity
   - _hybrid_rank() combines both signals (60% vector, 40% BM25)
   - Catches exact name/term matches that embeddings miss
   - Applied to both closet-first and direct drawer search paths

689/689 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Trimmed version of Milla's omnibus test_closets.py to only cover
features present in this PR stack (#784 lock, #788 closets, this
PR's entity/BM25/diary). Strip-noise tests will land with #785;
tunnel tests will land with the tunnels PR.

16/16 pass.

Co-Authored-By: MSL <[email protected]>

Adds active tunnel creation alongside passive tunnel discovery.

Passive tunnels (existing): rooms with the same name across wings.
Explicit tunnels (new): agent-created links between specific
locations. "This API design in project_api relates to the database
schema in project_database."

New functions in palace_graph.py:
- create_tunnel() — link two wing/room pairs with a label
- list_tunnels() — list all explicit tunnels, filter by wing
- delete_tunnel() — remove a tunnel by ID
- follow_tunnels() — from a room, find all connected rooms in
  other wings with drawer content previews

New MCP tools:
- mempalace_create_tunnel
- mempalace_list_tunnels
- mempalace_delete_tunnel
- mempalace_follow_tunnels

Tunnels stored in ~/.mempalace/tunnels.json (persists across
palace rebuilds). Deduplicated by endpoint pair.

689/689 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Appended from Milla's omnibus test_closets.py — covers create,
list, delete, dedup, and follow_tunnels behavior. 21/21 pass.

Co-Authored-By: MSL <[email protected]>

When a closet hit leads to a source file with many drawers, grep each
chunk for query terms and return the BEST-MATCHING chunk + 1 neighbor
on each side, instead of dumping the whole file truncated at
MAX_HYDRATION_CHARS. Result now includes drawer_index and
total_drawers so callers can request adjacent drawers explicitly.

Extracted from Milla's commit 935f657 which bundled drawer-grep with
closet_llm (deferred pending LLM_ENDPOINT refactor) and fact_checker
(separate PR). Ported only the searcher.py change.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

fact_checker.py verifies text for contradictions against locally stored
entities and KG facts. Catches similar-name confusion (Bob vs Bobby),
relationship mismatches (KG says husband, text says brother), and
stale facts (KG valid_from/valid_to).

No hardcoded facts. No network calls. Reads:
- ~/.mempalace/known_entities.json
- KnowledgeGraph SQLite

Usage:
  from mempalace.fact_checker import check_text
  issues = check_text("Bob is Alice's brother", palace_path)

  # CLI
  python -m mempalace.fact_checker "text" --palace ~/.mempalace/palace

Extracted from Milla's commit 935f657 which bundled this with
closet_llm (deferred) and drawer-grep (PR #791). Ported only
fact_checker.py — verified no network / API imports.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Adds mempalace/closet_llm.py as an OPTIONAL path for richer closet
generation. Regex closets remain the default and cover the local-first
promise; users who want LLM-quality topics can bring their own endpoint.

Configuration (env or CLI flag):
  LLM_ENDPOINT — OpenAI-compatible base URL (required)
  LLM_KEY      — bearer token (optional; local inference skips this)
  LLM_MODEL    — model name (required)

Works with Ollama, vLLM, llama.cpp servers, OpenAI, OpenRouter, and any
other provider that speaks OpenAI-compatible /chat/completions. Zero new
dependencies — uses stdlib urllib.

Replaces the original Anthropic-SDK-hardcoded version of this module
from Milla's branch (commit 935f657). Same prompt, same parsing, same
regenerate_closets flow; only the transport was generalised so the
feature doesn't lock users into a specific vendor or require API keys
for core memory operations (CLAUDE.md, "Local-first, zero API").

Includes 13 unit tests covering config resolution, request shape,
auth-header omission when no key is set, code-fence stripping, and
missing-config error path. All mocked — zero network calls in tests.

Co-Authored-By: MSL <[email protected]>

…te (#795)

ChromaDB defaults HNSW index to L2 (Euclidean) distance, but
MemPalace scoring uses 1-distance which requires cosine (range 0-2).
Add metadata={"hnsw:space": "cosine"} to the 4 production and 3 test
call sites that were missing it.

Closes #218

This PR introduces a standard SECURITY.md policy file to the repository. 

While reviewing the codebase, I noticed there wasn't a defined channel for the private, responsible disclosure of security vulnerabilities. Adding this policy helps protect the project by guiding researchers to report bugs privately rather than in public issues. 

I highly recommend merging this and enabling GitHub's "Private Vulnerability Reporting" feature in your repository settings. I currently have some security findings I would like to share with the maintainers securely once a private channel or contact method is established.

Commit 6614b9b bumped pyproject.toml to 3.2.0 but missed
mempalace/version.py, breaking test_version_consistency on
every PR's CI. This syncs them.

fix: sync version.py to 3.2.0

Adding the per-file lock + double-checked file_already_mined() in the
previous commit pushed mine_convos cyclomatic complexity from 25 to 26,
just over ruff's max-complexity threshold. Hoist the locked critical
section into _file_chunks_locked() so the outer loop stays within
budget. No behavior change.

Add blank lines after inline imports in mine_lock. Pure formatting.

fix: file-level locking to prevent multi-agent duplicate drawers

… Code JSONL

The initial strip_noise() regressed on three fronts when audited against
adversarial user content — each verified with executable repros against
the cherry-picked code:

  1. `<tag>.*?</tag>` with re.DOTALL span-ate across messages: one
     stray unclosed <system-reminder> anywhere in a session merged with
     the next closing tag, silently deleting everything between them
     (including full assistant replies).
  2. `.*\(ctrl\+o to expand\).*\n?` nuked entire lines of user prose
     whenever a user happened to document the TUI shortcut.
  3. `Ran \d+ (?:stop|pre|post)\s*hook.*` with IGNORECASE ate the
     second sentence from "our CI has a stop hook ... Ran 2 stop hooks
     last week" — legitimate user commentary.

These are unambiguous violations of the project's "Verbatim always"
design principle.

Fixes:

- All tag patterns are now line-anchored (`(?m)^(?:> )?<tag>`) and their
  body forbids crossing a blank line (`(?:(?!\n\s*\n)[\s\S])*?`), so a
  dangling open tag cannot eat neighboring messages.
- `_NOISE_LINE_PREFIXES` are line-anchored and case-sensitive — user
  prose mentioning "CURRENT TIME:" mid-sentence is preserved.
- Hook-run chrome requires `(?m)^`, explicit hook names (Stop,
  PreCompact, PreToolUse, etc.), and no IGNORECASE.
- "… +N lines" is line-anchored.
- "(ctrl+o to expand)" only matches Claude Code's actual collapsed-
  output chrome shape `[N tokens] (ctrl+o to expand)`; a bare
  parenthetical in user prose stays intact.

Scope:

- `strip_noise()` is no longer called on every normalization path.
  Only `_try_claude_code_jsonl` invokes it, per-extracted-message — so
  Claude.ai exports, ChatGPT exports, Slack JSON, Codex JSONL, and
  plain text with `>` markers pass through fully verbatim. Per-message
  application also makes span-eating structurally impossible.

Tests:

- 15 new tests in test_normalize.py pin the boundary: 6 guard user
  content that must survive (each of the adversarial repros), 9 assert
  real system chrome is still stripped. All pass; full suite 702 pass
  (2 failures are the unrelated pre-existing version.py bug, cleared
  by #820).

Known limitation (not fixed here): convo_miner.py does not delete
drawers on re-mine, so transcripts mined before this PR keep noise-
filled drawers until the user manually erases + re-mines. Proper fix
needs a schema-version field on drawer metadata + re-mine trigger —
out of scope for this PR.

…ema gate

Without this, the strip_noise improvement only helps new mines. Every
user who had already mined Claude Code JSONL sessions would keep their
noise-polluted drawers forever, because convo_miner's file_already_mined
skip short-circuits before re-processing.

Adds a versioned schema gate so upgrades propagate silently:

- palace.NORMALIZE_VERSION=2 — bumped when the normalization pipeline
  changes shape (this PR's strip_noise is the v1→v2 bump).
- file_already_mined now returns False if the stored normalize_version
  is missing or less than current, triggering a rebuild on next mine.
- Both miners stamp drawers with the current normalize_version.
- convo_miner now purges stale drawers before inserting fresh chunks
  (mirrors miner.py's existing delete+insert), extracted into
  _file_convo_chunks helper to keep mine_convos under ruff's C901 limit.

User experience: upgrade mempalace, run `mempalace mine` as usual, old
noisy drawers get silently replaced with clean ones. No erase needed,
no "you need to rebuild" changelog footgun.

Tests:
- test_file_already_mined_returns_false_for_stale_normalize_version —
  pins the version gate contract for missing/v1/current.
- test_add_drawer_stamps_normalize_version — fresh project-miner drawers
  carry the field.
- test_mine_convos_rebuilds_stale_drawers_after_schema_bump — end-to-end
  proof that a pre-v2 palace gets silently cleaned on next mine, with
  orphan drawers purged and NOT skipped.

Existing test_file_already_mined_check_mtime updated to include the
new field; all other tests unaffected.

Non-trivial merge in convo_miner.py: this branch's _file_convo_chunks
(purge stale + upsert with normalize_version) and develop's
_file_chunks_locked (mine_lock + double-checked file_already_mined)
both touched the same critical section. Combined into a single
_file_chunks_locked helper that does lock → double-check → purge →
upsert, preserving both the multi-agent safety guarantee from #784
and the schema-rebuild contract from this PR.

Also folds develop's mine_lock import into both miner.py and
convo_miner.py alongside NORMALIZE_VERSION.

707/707 tests pass, ruff + format clean under CI-pinned 0.4.x.

fix: strip system tags, hook output, and Claude UI chrome from drawers

The save hook and precompact hook were telling the agent to write
diary entries, add drawers, and add KG triples IN THE CHAT WINDOW.
Every line written stays in conversation history and retransmits on
every subsequent turn — ~$1/session in wasted tokens.

Fix: hooks now say "saved in background, no action needed" and use
decision: allow instead of block. The agent continues working without
interruption. All filing happens via the background pipeline.

Also updated hooks README with:
- Known limitation: hooks require session restart after install
- Updated cost section: zero tokens, background-only

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

fix: stop hooks from making agents write in chat — save tokens

Merges develop (#820 version sync, #785 strip_noise + NORMALIZE_VERSION,
#784 file locking) and addresses six concerns surfaced during PR review
of the closet feature:

1. Closet append-on-rebuild bug — upsert_closet_lines used to APPEND to
   existing closets (mismatched the doc's "fully replaced" promise). With
   NORMALIZE_VERSION rebuilds on develop, this would have stacked stale
   v1 topics on top of fresh v2 content forever. Fix:
   - Drop the read-and-append branch from upsert_closet_lines (now a pure
     numbered-id overwrite).
   - Add purge_file_closets(closets_col, source_file) helper that wipes
     every closet for a source file by where-filter.
   - process_file calls purge_file_closets before upsert on every mine,
     mirroring the existing drawer purge.

2. Searcher returned whole-file blobs from the closet path while the
   direct path returned chunk-level drawers. Refactored:
   - _extract_drawer_ids_from_closet parses the `→drawer_a,drawer_b`
     pointers out of closet documents.
   - _closet_first_hits hydrates exactly those drawer IDs (chunk-level),
     not collection.get(where=source_file) (which returned everything).
   - Same hit shape as direct-search path; both now carry matched_via.

3. max_distance was bypassed on the closet path. Now applied per-hit;
   when every closet candidate gets filtered, _closet_first_hits returns
   None and the caller falls through to direct drawer search.

4. Entity extraction caught sentence-starters like "When", "The",
   "After" as proper nouns. Added _ENTITY_STOPLIST (~40 common false
   positives + day/month names + role words). Real names like Igor /
   Milla still survive — covered by tests.

5. CLOSETS.md drifted from the code (claimed "replaced via upsert" but
   code appended; claimed BM25 hybrid that doesn't exist; claimed a
   10K char hydration cap that wasn't enforced). Rewritten to describe
   what actually ships, with explicit notes on the BM25 / convo-closet
   follow-ups.

6. Zero tests for ~250 lines. Added tests/test_closets.py with 17 cases:
   - build_closet_lines: pointer shape, header extraction, stoplist
     filtering (with regression case for "When/After/The"), real-name
     survival, fallback-line guarantee, drawer-ref slicing.
   - upsert_closet_lines: pure overwrite semantics (regression for the
     append bug), char-limit packing without splitting lines.
   - purge_file_closets: scoped to source_file, doesn't touch others.
   - End-to-end miner rebuild: re-mining a file with fewer topics fully
     purges leftover numbered closets from the larger first run.
   - _extract_drawer_ids_from_closet: parsing + dedup edge cases.
   - search_memories closet-first: fallback when empty, chunk-level
     hits with matched_via, no whole-file glue, max_distance enforced.

Merge resolutions: miner.py imports combined NORMALIZE_VERSION/mine_lock
from develop with the closet helpers from this branch. process_file
auto-merged cleanly (closet block sits inside develop's lock body).

724/724 tests pass. ruff + format clean under CI-pinned 0.4.x.

#819)

feat: closet layer — searchable index pointing to drawers

chore: forward closet layer (#788) into develop

…-caching-3001788084232137906

⚡ Optimize entity detection with regex caching and pre-compilation

docs: fix stale org URLs in website and plugin manifests (#787)

* fix: README audit — match every claim to shipped code + add hall detection

TDD audit: wrote 42 tests verifying README claims against codebase.
Fixed all 7 failures:

1. Tool count: 19 → 29 (10 tools were undocumented)
2. Added tool table rows for tunnels, drawer management, system tools
3. Version badge: 3.1.0 → 3.2.0
4. dialect.py file reference: "30x lossless" → "AAAK index format for closet pointers"
5. Wake-up token cost: "~170 tokens" → "~600-900 tokens" (matches layers.py)
6. pyproject.toml version in project structure: v3.0.0 → v3.2.0
7. Hall detection: added detect_hall() to miner.py — drawers now tagged
   with hall metadata so palace_graph.py can build hall connections

New code:
- miner.py: detect_hall() — keyword scoring against config hall_keywords,
  writes hall field to every drawer's metadata
- tests/test_hall_detection.py — 12 TDD tests (written before code)
- tests/test_readme_claims.py — 42 TDD tests verifying README accuracy

859/859 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix: resolve ruff lint — unused imports and variables

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* style: ruff format with CI-pinned 0.4.x

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix: use conftest fixtures in hall tests for Windows compat

Windows CI fails with NotADirectoryError when ChromaDB tries to
write HNSW files in short-lived TemporaryDirectory. Use conftest
palace_path and tmp_dir fixtures instead — same pattern as all
other tests that touch ChromaDB.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

* fix: address Igor's review — convo_miner halls, cached config, markdown typo

TDD: wrote tests for convo_miner hall metadata and config caching
BEFORE verifying the code changes.

1. README markdown typo: extra ** in wake-up token row (line 195)
2. convo_miner.py: added _detect_hall_cached() — conversation
   drawers now get hall metadata (was missing, Igor caught it)
3. miner.py + convo_miner.py: cached hall_keywords at module level
   so config.json isn't re-read per drawer during bulk mine
4. New tests: TestConvoMinerWritesHalls, TestDetectHallCaching

861/861 tests pass. ruff clean.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

Fix: set cosine distance metadata on all collection creation sites

Prepare develop for the 3.3.0 release cycle.

Version bumps:
- mempalace/version.py: 3.2.0 -> 3.3.0
- pyproject.toml: 3.2.0 -> 3.3.0
- README.md: pyproject.toml label and shields.io badge
- uv.lock: mempalace 3.0.0 -> 3.3.0 (also fills in resolved dev/extras)

CHANGELOG.md:
- Close out the stale [Unreleased] section as [3.2.0] - 2026-04-12
  (v3.2.0 was tagged on that date but the release flip was never made)
- Add a fresh [Unreleased] - v3.3.0 section covering the 49 commits
  since v3.2.0: closet layer, BM25 hybrid search, entity metadata,
  diary ingest, cross-wing tunnels, drawer-grep, offline fact checker,
  LLM-based closet regen, hall detection, cosine-distance fix,
  multi-agent locking, README audit, etc.
- Adopt Keep a Changelog + SemVer framing
- Add version compare reference links at the bottom
- Fix stale milla-jovovich/mempalace preamble URL to MemPalace/mempalace

chore(release): bump to 3.3.0 and curate CHANGELOG

fix(website): update vitepress base url for custom domain

TDD: test written first, failed, then fixed.

Problem: save hook says "saved in background" but MEMPAL_DIR defaults
to empty, so nothing actually mines. Users get no auto-save despite
the hook firing every 15 messages.

Fix: use TRANSCRIPT_PATH (received from Claude Code in the hook's
JSON input) to discover the session directory. Mine that directory
automatically. MEMPAL_DIR is still supported as override but no
longer required.

Also fixed: bare python3 → $(command -v python3) for nohup safety.

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

Bring back the main-only content that develop has been missing:
- pyproject.toml chromadb upper-bound removal (#690)
- CHANGELOG [3.2.0] Packaging subsection (#690, #761)
- CONTRIBUTING.md fork-first clone instructions
- mempalace/hooks_cli.py richer block-reason strings (from #666,
  still used by the Python hook invocation path)
- integrations/openclaw/SKILL.md version bump to 3.3.0

Plus the v3.3.0 release commit itself (4aa7e1e) and the legacy
main-only commits (#666, #690, v3.2.0 finalization) for history.

Resolves the main → develop drift that caused PR #838's conflicts.
Going forward, back-merging main to develop after each release
will prevent the same pattern.

Single conflict in CHANGELOG.md resolved by taking main's version
(the Packaging subsection under [3.2.0]).

Docs deploy to GitHub Pages from develop for faster iteration cycles.
Main was failing the deploy step with "Branch 'main' is not allowed to
deploy to github-pages due to environment protection rules" on every
release merge (v3.2.0, v3.3.0) — noise without signal, since docs
weren't meant to serve from main anyway.

Removes main from both the push trigger and the deploy-job guard.
Develop continues to deploy as before; manual dispatch still works.

sync: main → develop (post v3.3.0 release)

ci: serve docs from develop only

Prerequisite for RFC 001 (plugin spec, #743). Removes every direct
`import chromadb` outside the ChromaDB backend itself so the core
modules depend only on the backend abstraction layer.

Extends ChromaBackend with make_client, get_or_create_collection,
delete_collection, create_collection, and backend_version. Adds
update() to the BaseCollection contract. Non-backend callers
(mcp_server, dedup, repair, migrate, cli) now go through the
abstraction; tests patch ChromaBackend instead of chromadb.

With this landed, the RFC 001 spec can be enforced and PalaceStore
(#643) can ship as a plugin without touching core modules.

refactor: route all chromadb access through ChromaBackend (v4 prep)

Aligns marketplace.json and both plugin.json files with version.py /
pyproject.toml (already at 3.3.0) so `/plugin update` reflects the
v3.1.0/v3.2.0/v3.3.0 tags that had been landing without manifest bumps.

Also updates marketplace.json `owner.url` from the stale
github.com/milla-jovovich path to the current github.com/MemPalace org.

Refs #874

Fails a tag push if `vX.Y.Z` does not match `mempalace/version.py` (the
single source of truth per CLAUDE.md), and fails PRs that touch any
version file without keeping all five in sync (pyproject.toml,
version.py, .claude-plugin/marketplace.json, .claude-plugin/plugin.json,
.codex-plugin/plugin.json).

Prevents the class of bug described in #874, where v3.1.0/v3.2.0/v3.3.0
tags all landed pointing at commits that still carried manifest version
3.0.14, blocking `/plugin update` for end users.

Refs #874

Tags matching `vX.Y.Z-*` (e.g. v3.4.0-rc1, v1.0.0-beta.2) are treated as
internal/staging builds. They skip the tag-vs-manifest check because
pre-releases do not flow to end users via `/plugin update`, which reads
the manifest on the default branch.

Stable tags `vX.Y.Z` still require all five version sources to match
exactly, so the protection against the #874 drift remains intact. The
cross-file consistency check on PRs is unchanged — all manifests must
still agree with mempalace/version.py whenever any version file moves.

Adds website/public/CNAME containing `mempalaceofficial.com` so the
VitePress build output always includes /CNAME in the Pages artifact.
Without this, the custom-domain setting is only held in the repo's
Pages API config — if it ever drifts (manual edit, org move, workflow
change), the site reverts to <org>.github.io with no record in source.

Note: this does not fix the current site outage. The root cause is DNS
— mempalaceofficial.com has no A/AAAA/CNAME records pointing at GitHub
Pages IPs. That has to be fixed at the registrar. This commit is the
belt-and-suspenders so that once DNS is back, the domain is pinned in
source and the next workflow refactor can't accidentally drop it.

fix: align plugin manifests with release tags and guard future drift (#874)

fix: ship CNAME in Pages build to pin mempalaceofficial.com

fix: update stale org URLs in pyproject.toml and README (#787)

…nnel

Builds on @Yorji-Porji's draft by fixing three issues before it lands:

- Replace the `< 1.0.0` placeholder table with MemPalace's actual
  support policy: current major (3.x) receives fixes, 2.x and earlier
  do not.
- Remove the `[Insert Maintainer Email Here]` placeholder and the
  email fallback. GitHub Private Vulnerability Reporting is enabled
  on this repo; the policy points there exclusively so there is no
  risk of a researcher emailing a dead address.
- Drop the meta-note ("Adjust the table above…") that was an
  instruction to the maintainer, not policy text.

Structure, triage timelines, and credit language are kept as drafted.

Create SECURITY.md