docs(skills): capture commit + pr-fixup learnings from #935 (#943)

.agents/skills/commit/SKILL.md

@@ -37,6 +37,7 @@ type: lowercase description
 - Include PR/issue number when relevant: `feat: add release notes (#295)`
 - Breaking changes: add `!` after type: `feat!: remove legacy API`
 - Keep the first line under 72 characters
+- **Body lines must be ≤100 characters** (commitlint `body-max-line-length`). Hard-wrap bullet points before committing; long URLs or prose lines that exceed 100 chars will fail the hook with `body's lines must not be longer than 100 characters`. If a HEREDOC body fails, re-wrap and create a *new* commit — do not amend.
 
 ## Examples
 

.agents/skills/pr-fixup/SKILL.md

@@ -245,6 +245,12 @@ After the push, CI restarts and bots may re-review. Delegate to `pr-poller` agai
 - If new review comments appeared after the push → loop back to task 3.
 - If the poller hit its cap (`recommendation:` mentions "timed out") → surface the remaining pending items to the user and stop.
 
+**Force-push (rebase) can re-open previously resolved inline threads.** GitHub treats the new commit's diff as a fresh review surface, so threads you already replied-to-and-resolved may come back unresolved with their original bodies. Before re-fixing, fetch the comments and check the body — if the issue is already addressed in the new tip, reply "Already fixed in `<sha>`" and resolve again rather than re-implementing.
+
+**Mergeable status lags after a force-push.** `gh pr view --json mergeable` can show `CONFLICTING` / `mergeStateStatus: DIRTY` for ~5-10s while GitHub recomputes against the new tip. Wait briefly before deciding there's a real conflict, and confirm with `git fetch origin main && git diff --name-only HEAD origin/main` locally.
+
+**Polling that times out is often a "main moved" signal.** A 20-min E2E window is long enough for `main` to ship one or two PRs. Before the next iteration, run `git fetch origin main && git log HEAD..origin/main --oneline` — a non-empty result means a rebase is coming. Rebase, force-push, and re-poll once rather than chasing flaky test reruns.
+
 Cap re-check loops at **3 iterations** to prevent runaway sessions. After 3, surface the remaining state to the user and stop.
 
 Mark task 6 as completed.