…HNSW fixes

Bring in 29 commits from upstream/develop since the last merge (2026-04-23):

Major absorbed changes:
- MemPalace#976 (Felipe Truman): HNSW graph corruption fix, mine_global_lock for
  fan-out, MAX_PRECOMPACT_BLOCK_ATTEMPTS=2 for /compact deadlocks. Closes
  MemPalace#974/MemPalace#965/MemPalace#955; likely resolves MemPalace#1172 too.
- MemPalace#1179 (Igor): CLI mempalace search routes through _hybrid_rank,
  legacy-metric warning + _warn_if_legacy_metric, invariant tests on
  hnsw:space=cosine across all 5 collection-creation paths.
- MemPalace#1180/MemPalace#1183/MemPalace#1184: cross-wing topic tunnels, init mine UX, --auto-mine.
- MemPalace#1185 (perf/batched-upsert-gpu): batched ChromaDB upserts, GPU device
  detection via mempalace/embedding.py.
- MemPalace#1182: graceful Ctrl-C during mempalace mine.
- MemPalace#1168: tunnel permissions security fix.

Conflict resolutions (8 files):
- searcher.py: kept fork's CLI delegation through search_memories (cleaner
  single-source-of-truth path); upstream's inline-retrieval branch dropped.
  Merged upstream's print formatting (cosine= + bm25=) with fork's
  matched_via reporting from sqlite BM25 fallback.
- backends/chroma.py: kept fork's _BLOB_FIX_MARKER + palace_path arg to
  ChromaCollection (MemPalace#1171 write lock); merged upstream's **ef_kwargs
  (embedding_function support from MemPalace#1185). Removed duplicate
  _pin_hnsw_threads (fork already cherry-picked Felipe's earlier).
- mcp_server.py: kept fork's palace_path arg + upstream's clearer comment
  on hnsw:num_threads=1 rationale.
- miner.py: took upstream's serial mine() flow (mine_global_lock + Ctrl-C),
  RESTORED fork's strict detect_room — substring matching from upstream
  breaks fork-only test_detect_room_priority1_no_substring_match. Added
  `import re` for word-boundary regex matching. Fork-ahead concurrent
  mining (workers=, ThreadPoolExecutor from 5cd14bd) is dropped — daemon
  migration deprioritizes local concurrent mining; can re-port if needed.
- CHANGELOG.md: combined fork's segfault-trio narrative with upstream's
  v3.3.4 release notes.
- HOOKS_TUTORIAL.md: took MEMPALACE_PYTHON env var name (fork README was
  stale; hooks already use this name per fork-ahead MemPalace#19).
- test_convo_miner_unit.py: took both contextlib + pytest imports.
- test_searcher.py: imported upstream's 3 new TestSearchCLI tests but
  skipped them with TODOs — they assume upstream's inline-retrieval CLI
  with simpler mocks. Rewrite needed for fork's delegated search_memories
  path (sqlite BM25 fallback + scope counting).

Test result: 1334 passed, 3 skipped (the upstream tests above), 3 warnings.

Implications for open fork PRs:
- MemPalace#1171 (cross-process write lock at adapter) becomes structurally
  redundant given MemPalace#976's mine_global_lock + daemon-strict serialization.
  Slated for close with thank-you to Felipe.
- MemPalace#1173/MemPalace#1177 still relevant (quarantine threshold + blob_seq marker).

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

)

Sync with upstream/develop via cherry-pick of 9 critical bugfixes:
- HNSW index bloat prevention (MemPalace#1191)
- SIGSEGV guards on collection reopen (MemPalace#1262, MemPalace#1289)
- blob-seq marker fast-path (MemPalace#1177)
- palace_graph None-metadata guard (MemPalace#1201)
- palace_graph security tunnels (MemPalace#1168)
- hyphenated wing name normalization (MemPalace#1197)
- searcher _tokenize None guard (MemPalace#1198)
- mcp_server diary topic sanitize (MemPalace#936)

Tests: 1459 default + 113 benchmark + 6/7 stress all pass.
(random-kill stress test was failing on dev pre-merge; not regressed.)