Follow dispatched fixes to the merge (0.9.7)

[iamwhatever]

Summary

Dispatched fixes are now followed to the merge. Before this, Re-analyze only saw a dispatched fix when its Slack thread moved, and nothing read the PR, so a merged fix stayed triaged under Fixes in flight.

• PR state read (backend/github_state.py, called from watch.poll_once after the digest step): gh pr view <url> --json state,mergedAt,closedAt,isDraft with the owner's own gh, read-only, asyncio.to_thread(subprocess.run, timeout=20). At most 10 URLs a cycle, oldest-checked first, each at most every 30 min, never again once merged/closed. gh missing / logged out / rate-limited / timed out: unknown with a short why, no read for 1 h. Per-URL readings in <data>/pr_states.json; each item gets fix_handoff.pr_state = {state, at, checked_at, merged_at?, why?}. On the first merged: one dispatch event PR #N merged and a possibly_resolved flag (fix PR #N merged) for the Thread Watcher, unless one is already there. Nothing sets resolved, regenerates a draft, posts, or writes to GitHub.
• Re-analyze set: store.needs_reanalysis is also true when pr_state is merged/closed and pr_state_seen_at is older than pr_state.at. send_reanalyze stamps pr_state_seen_at. The prompt prints PR <url> · merged 2026-09-30 / · open / · closed, not merged and the merged/closed rule.
• Record tool: a fix_handoff carrying pr_state or pr_state_seen_at is refused; a Lead rewrite keeps both; a new dispatch clears both.
• Board: a merged fix is back in Needs a decision as Fix merged · PR #N with Done; its line reads Dispatched · <title> · PR #N merged ✓; Fixes in flight leaves it out and shows the other PRs' state; the Ledger row tags it fix merged / fix PR closed. The Re-analyze count includes it.
• Brief v9, README (both halves), desk/CHARTER.md, desk/CONTRACT.md, app.json 0.9.7.

Deviation from the request: the request said the Lead should "set possibly_resolved". The record tool has no field for that (only clear_possibly_resolved), and an unknown field refuses the whole row. So the gateway sets the flag on the merge, the same way the poller flags a thread, and the prompt and brief tell the Lead to leave that flag to the Watcher or set resolved when the thread also confirms. /now has no dispatched-fix summary today, so nothing was added there.

Tested

• python -m pytest tests -q -p no:cacheprovider: 354 passed (25 new in tests/test_pr_state.py, all with an injected fake gh runner; an autouse fixture fails any real gh call).
• npm run build: clean; ui/dist/index.mjs rebuilt.
• docs/screenshots/capture/shoot.mjs: all checks pass, including the new fix-merged check (row reads PR #412 merged, link, Done only, Re-analyze 3 stale, fold excludes it and shows PR #418 open, Ledger tag fix merged). New frame docs/screenshots/fix-merged.png.