merge-queue triage: excerpt the failure REASON, and aggregate same-signature ejections into one anchor issue

.github/workflows/lint.yml

@@ -1043,6 +1043,46 @@ jobs:
  node scripts/check-cross-repo-closer-outcome.mjs --self-test
  node scripts/check-cross-repo-closer-outcome.mjs
 
+ # Merge-queue triage outcome contract (#10128, over the #4859 bot).
+ # merge-queue-triage.yml carries ~450 lines of inline github-script that
+ # only ever runs on a RED merge_group build — a condition nobody can
+ # produce on demand, so its two 2026-08-20 limbs would otherwise be
+ # unexercised code. This step is the exercise, on the same method as the
+ # cross-repo closer step above: the shipped script is extracted from the
+ # YAML with a real parser (never retyped) and run under doubles the way
+ # actions/github-script runs it, as one AsyncFunction body. No network.
+ #
+ # What it holds: (1) the excerpt names the failure REASON beside the FAIL
+ # line, driven against REAL captured vitest logs of the incident's own
+ # test file — one timeout, one assertion, byte-identical FAIL lines and
+ # opposite diagnoses, which is the confusion that produced a confidently
+ # wrong card (#10112) and cost a whole dispatch; and (2) the cross-PR
+ # aggregation files exactly ONE anchor issue at >= 2 DISTINCT PRs,
+ # REFRESHES it on the next ejection instead of filing a second, and files
+ # none for two different keys or for one PR ejecting twice. The refresh
+ # leg is driven as a PAIR — run 2's world is built from run 1's output —
+ # because idempotency is a property of the pair and a hand-written marker
+ # would prove each half while leaving the two runs free to disagree.
+ #
+ # Its --self-test runs first and is the half that stops the battery
+ # rotting into decoration: it mutates the shipped script fourteen ways —
+ # drop the reason lookahead, test the FAIL pattern before the reason
+ # pattern (which silently loses every assertion), count runs instead of
+ # distinct PRs, always create instead of refreshing, drop the sighting
+ # markers, downgrade each anti-no-op announcement to an info line, and
+ # more — and requires the battery to go RED for each, naming the scenario
+ # that catches it. A mutation whose anchor no longer exists is a failure
+ # too, so a rewrite of the workflow cannot leave the mutations silently
+ # matching nothing.
+ #
+ # Invoked as `node` rather than through a `pnpm check:*` alias, same
+ # reason as the step above: root package.json is declared territory of
+ # the @changesets/cli v3 migration lane (#9465) while it runs.
+ - name: Merge-queue triage outcome contract
+ run: |
+ node scripts/check-merge-queue-triage-outcome.mjs --self-test
+ node scripts/check-merge-queue-triage-outcome.mjs
+
  # Shard positive-attestation gate (#6082). ci.yml's two aggregate gates
  # used to decide from one `needs.<matrix>.result` word, which cannot carry
  # three shards' verdicts: run 31120902911 read the undocumented