[Birfy]

Fixes #534, Fixes #538, Fixes #567

Risk: T2 (plugins/timeline/**).

What

One PR for the three timeline read-model proposals that all touch the same return line of
plugins/timeline/src/window.js and the same docs/subsystems/timeline.md row, so the owner
gets one PASS and one click instead of three rebases:

• stuck: the open request arrows, worst first (waitedMs floored at 0, capped at 20) — Timeline: list the requests waiting longest #534 / Proactive reminders 1/3 follow-up: quiet hours, mute, waiting-too-long #469.
• toolUse: per-Bot tool calls by cleaned name with their failure counts — Timeline: which tools each Bot used, and how often they failed #538 / Plugin and App connect: catalog, guided auth, and a fast developer scaffold (cf. Grok Bot connectors) #359.
• timeline/health: new pure plugins/timeline/src/health.js (buildHealth(window)) plus the read-only endpoint, per-Bot signals and flags and a team ok — Timeline: a team-health endpoint (#357) #567 / Performance dashboard: Nightly CI metrics for FlyBot smoothness #357.

Both new window fields are additive; the window version and every existing field are unchanged.
Host-side has no copy of this code (the timeline is a plugin), so patches/ds-bot/ is untouched
and ds-bot-patches.mjs check still passes.

Supersedes

Closes #535, #539 and #568 as superseded: their content, review and tests are all carried here,
including the authorship trail in the three PRs. Thanks to HugoXK for the three originals.

Checks (run by the maintenance round on this tree)

• ds-bot-patches.mjs check — OK (10 patches, core == ds-bot + patches).
• check-arch-docs.mjs with ARCH_DOCS_BASE=HEAD~1 — OK (7 changed files).
• changelog.mjs check — OK (12 fragments).
• plugins/timeline tests — 101/101.
• scripts/lint-plugins.mjs timeline — 0 errors, 8 warnings (all pre-existing).
• TDD: with window.js and timeline.js at the base commit and health.js absent, 3 tests fail
  (the two new window tests and the health test file); all pass with the change.

Not run: one-shot npm run verify (the container OOMs at 2 GiB), full core suite, smoke, Desktop.

[Birfy]

Verdict: PASS at d131a1e

Tip SHA: d131a1e3c0174d1036b425f81ceeb47dbe7cd2a7
This is the combined replacement for #535 / #539 / #568, built by the maintenance round as the owner asked, so the three proposals become one PASS and one click. The three originals are closed as superseded and their content, tests and wording are all here.
Diff (7 files, +148 -3): `window.js` gains `stuck` (open request arrows, worst first, `waitedMs` floored at 0, capped at 20) and `toolUse` (per-Bot tool calls by cleaned name with failure counts, capped at 20 per Bot) as two additive blocks plus two names on the existing return line; new `plugins/timeline/src/health.js` (`buildHealth(window)`, pure) with its `timeline/health` endpoint wired in `timeline.js` and `dispose`; the tests from both originals; the `timeline.md` row merged into one sentence and the new `health.js` row and endpoint bullet; one changelog fragment.
Host side has no copy of the timeline (it is a plugin), so `patches/ds-bot/` is untouched and the patches check still passes; the window version and every existing field are unchanged, so nothing that reads the window today breaks.
Ran at the tip: CI all green (tests-ok, plugins social/tree/timeline, package, Node 24). On this tree: `ds-bot-patches.mjs check` OK (10 patches, core == ds-bot + patches), `check-arch-docs.mjs` with `ARCH_DOCS_BASE=HEAD~1` OK (7 files), `changelog.mjs check` OK, `plugins/timeline` 101/101, `scripts/lint-plugins.mjs timeline` 0 errors / 8 pre-existing warnings, TZ=UTC.
TDD: with `window.js` and `timeline.js` at the base commit and `health.js` absent, 3 tests fail (both new window tests and the health file); all 101 pass with the change.
Merge state: clean against main 33fb55ed and against every other open PR.
Not run: one-shot `npm run verify` (2 GiB OOM), full core suite, smoke, Desktop.
Tier: **T2** (`plugins/timeline/**`). The owner's own click in the GitHub UI is the approval and this PASS must sit on the tip; I do not approve or merge it myself. Any new commit voids this PASS.