fix(agent): write a session file with its first message (plan decision 17) - #25

…used in pi-shell (plan decision 10) (#27)

* refactor(tui): delete the goal prompt templates and the research script that nothing loads

Nothing in the tree names these 15 files any more (git grep by file name: no hit).
The last code that loaded them was removed with the Rust agent runtime in
455527c (#7); the files stayed, and rustc cannot see a file that no `include_str!`
names, so no warning reported them.

pi-shell/src/session/templates/ (14 Markdown prompt templates for the goal
mode) and pi-shell/src/session/workflows/deep_research.rhai (584 lines).
15 files, 1,033 lines. No Rust code changes.

* refactor(tui): delete the dead units session::worktree and session::helpers of pi-shell

The call graph (scripts/tui_callgraph.py units) reports both as dead: nothing in the
consumer build (pi-pager-bin, pi-pager-minimal, pi-update) reaches them. rustc does not
warn, because what they hold is `pub(crate)` or a re-export.

session::worktree (359 lines): a glob re-export of pi_workspace::worktree, two `From`
impls between the shell's WorktreeType and the workspace's (nothing calls them), and 24
tests of types and functions that live in pi-workspace (serde shapes, build_candidate_list,
BackgroundCopyContext, resolve_worktree_by_id_or_path).

session::helpers (3 files, 61 lines): comments, and two tests of string shapes.

The two `resolve_worktree_by_id_or_path` tests were the ones that opened worktrees.db in
whatever GROK_HOME held; they are gone with the unit. pi-shell tests: 864 -> 838.

pi_workspace::worktree has no user left in pi-shell after this; that is left for plan D.8.

* refactor(tui): remove the [storage] section from the pi-shell config

`[storage] cleanup_ttl_days` set how long old session files were kept. The code that
read it went with the session store (#26), and the pager keeps no session file now.
`StorageConfig` and the `storage` field of `Config` are deleted.

A config file that still has the section loads. The section is reported as
unrecognized, like any other unknown section: a new test pins that, and the
"valid config" test no longer lists the section.

`storage_mode` (the `--storage-mode` flag and `Config.storage_mode`) is a different
setting. This change does not touch it.

* refactor(tui): delete util::config::worktree of pi-shell

`util::config::worktree` holds a `WorktreeType` enum (with `FromStr` and a `From` impl for
`CreationMode`). Its one user was `session::worktree`, which the previous commit deletes. The
baseline `check` shows it: the glob re-export of the module is an unused import (1 warning;
the ceiling is 0).

`pi-workspace` and `pi-workspace-types` have their own `WorktreeType` and do not use this
one. The module has one test, `test_worktree_type_fromstr`; it goes with it. `pi-shell` has
no other reference to `pi_fast_worktree` now, so that dependency goes in the next commit.

* refactor(tui): remove the dependencies of pi-shell that no source file names

Ten dependencies of `pi-shell` are not named in any source file of the crate outside comments
(a text scan of `src/`, `tests/` and `build.rs`; the compiler has the last word):

- `[dependencies]`: `urlencoding`, `base64`, `pi-fast-worktree`, `pi-compaction-transcript`,
  `pi-workflow`, `tdigests`, and `nix` (unix only).
- `[dev-dependencies]`: `pretty_assertions`, `pi-test-utils`, `tokio-util`.

Eight lost their last user in #26 (the session store). `pi-fast-worktree` lost its last users in
`session::worktree` and `util::config::worktree` (this branch), and `tokio-util` in the tests of
`session::worktree`.

The dependency graph of `pi-pager-bin` goes from 980 to 970 packages on Linux: `pi-workflow` (a
crate of this workspace; no other crate depends on it now) and nine packages from the registry
(`tdigests`, `rhai`, `rhai_codegen`, `smartstring`, `thin-vec`, `const-random`,
`const-random-macro`, `crunchy`, `tiny-keccak`). `Cargo.lock` loses `tdigests` and ten
dependency lines. The other packages stay in the lock file, because `pi-workflow` is still a
member of the workspace. `THIRD-PARTY-NOTICES` loses 5 entries (it lists the packages that ship on
any platform; `tui_notices.py check`: 984 of 984).

* chore(tui): lower the ceilings of the baseline after the cleanup of pi-shell

- `[gates.residue]`: `leader` 245 -> 243 and `x.ai` 304 -> 297. The deletions of #26 removed
  those lines; `check` has said "lower the ceiling" since then.
- `[graph.max_nodes]`: 980 -> 970 packages on Linux (the dependency commit of this branch).
- `pi-shell` `reference_passed`: 864 -> 838. The tests of `session::worktree` (24, Unix only),
  `session::helpers` (2) and `util::config::worktree` (1) are gone, and one test is new (a
  `[storage]` section is reported as unrecognized). The ten references add up to 8,488 (8,514
  before).

A local run on Linux (WSL2) gives: `check` with 0 warnings, 970 packages, `leader` 243 and `x.ai`
297; the ten test suites 8,487 passed and 1 failed (the known `tmux_probe` test of
`pi-pager-render`); `tui_notices.py check` 984 of 984.

* docs: record plan r16 (the merge of #25 and #26, and what the session store left in pi-shell)

- CHANGELOG.md: the entry for the third cleanup of pi-shell (15 files, three modules, the
  [storage] setting, 10 dependencies). It also says that the earlier entry left
  `[storage] cleanup_ttl_days` for this one.
- docs/baselines/tui.md: current baseline r16 (tests 8,488, graph 970, `leader` 243, `x.ai` 297)
  and a column r16 in the table of sizes. The numbers are from local runs (WSL2); the CI numbers
  of PR #27 follow in a later commit.
- docs/baselines/archive/tui-history.md: the r16 paragraph, with the CI numbers of `7d82c27`.
- docs/baselines/tui-support.md: made again (`pi-shell` has 7 dead units, 1,008 lines, not 9 and
  1,388).
- Plan: status r16, next steps, decision 10, D.2, D.8 (new candidates: 7 dead units, the crate
  `pi-workflow`, `Config.storage_mode`, about 88 files that no code loads), D.9, a new open item
  "races between tests", the index and the revision list.
- Execution log: section 10.19, B.11 (how to repeat the checks) and the r16 revision entry.

* docs: record the CI result of PR 27 in the plan, the log and the baselines

`CI` (run 39193752450) and `TUI CI` (run 39193752451) pass on 6bd7db5.
`TUI CI`: 8,488 passed, 0 failed, 21 ignored; 970 packages in the graph;
`leader` 243, `x.ai` 297; 0 warnings. These are the numbers that section
10.19 of the execution log expected, so only the "to be added" line and
the timing bullet change, plus one sentence in each r16 entry.

The cargo test job took 17 m 34 s and the gates job 4 m 24 s. The tests
themselves took about 54 s of that time.

…to #31 (plan r19) (#33)

The owner asked for three things: merge the five open PRs (#27 to #31) into main with
`gh stack`, set the V0.6 milestone from the present state, and pause development for
1 to 2 days.

The merge is done (stack #32, `gh stack merge 32 --yes --squash`). main goes from
7d82c27 to b33017a with five squash commits. The tree of each commit is the tree of its
PR head. CI and TUI CI pass on b33017a (8,490 passed, 0 failed, 22 skipped).

The plan gets a new section "发布里程碑 V0.6": the scope (the 10 commits on main after
v0.5.0), six exit conditions with their state, the known issues (two are new), and what
is not in V0.6. It also gets the r19 status, the pause, and the fixed status of the
places that still said "waiting for merge" for #25 to #28. The execution log gets
section 10.22: the install of `gh stack` (the first download was cut short), the merge,
the check of the trees, CI on main, the milestone, the pause, and what is not verified.

The GitHub milestone v0.6.0 (#2) is created. It has no due date and no PRs, as v0.5.0.
No condition is met yet. Only documents change.