docs(agents): record Actions queue and merge procedure

AGENTS.md

@@ -42,9 +42,22 @@ The materialization contract is also covered by [`docs/doctoring/exact-artifact-
   target repository, and pull request number with `cancel-in-progress: true`;
   do not include the head SHA, because that prevents a new head from cancelling
   its predecessor. Non-PR triggers need an explicit collision-safe fallback.
+- Do not let a rerun of an older run ID re-enter the live PR group and cancel
+  newer evidence. Use the PR number only for the first attempt and fall back to
+  `github.run_id` for reruns, or reject the rerun through exact-live-head
+  admission before it can displace current work.
 - Put concurrency at workflow scope when queued jobs must be coalesced before a
   runner is admitted. Job-level concurrency cannot relieve a saturated runner
   queue because it is evaluated only after job admission.
+- Subscribe only to pull-request actions that can produce useful work. The
+  default review set is `opened`, `synchronize`, `reopened`, and
+  `ready_for_review`; do not add `converted_to_draft` or `closed` merely to run
+  a job-level false condition, because the workflow run still enters the
+  organization queue. Add a lifecycle action only when that workflow performs
+  an explicit, tested cleanup or state transition for it. That cleanup must
+  compare the live PR head and cancel only runs bound to a different head;
+  putting an unchanged-head draft or close event into the same PR concurrency
+  group would cancel current evidence rather than a superseded head.
 - Keep cleanup repository-local and event-driven. Do not restore an
   organization-wide queue sweep, polling `sleep`, or another scheduled scan to
   compensate for incorrect concurrency. Cancel only runs proven to belong to a