Batch doctor: a red merge batch with no single culprit #11293

The batch doctor now records a red that the merge queue narrows to one pull but finds only on top of pulls that landed first, and it still holds nothing for it. I did not build the "re-gate each member singly" step the issue also names. I did not use keep_plan; I had no such tool in this session.

The queue already bisects a red batch down to one pull (stacked prefixes, then leave-one-out). The doctor, though, only acted on the later re-gate, where the pull is alone. A pull that was red only on top of others left no record at all. That was the gap.

What changed

• src/checks/doctor.ts has a new noteRed(app, repo, pull, red, baseOid, together).

- Class: it classes the red (budget, infra or functional). - Record: it writes a maintenance_run row with action recheck. The batch field is base:head+#a,#b, so the members the pull was red with are named. - No hold: it never holds. With no pulls ahead of it, it does nothing.

• src/crew/autonomy.ts (handBack) calls noteRed on a first red that has together non-empty. The re-gate path is unchanged.
• Hold with the exact test: when the re-gate carries the pull alone and the red reproduces, the existing treatRed holds it and comments the exact failing test, file, error line and bun test ./file.
• docs/features/batch-doctor.md has a short paragraph on this. test/doctor-culprit.test.ts has a test that the run is recorded with its members, nothing is held, and an empty together records nothing.

Checks

• bun test test/doctor-*.test.ts: 20 pass.
• bun x tsc --noEmit: clean.
• bun scripts/gate.ts: no output.
• I did not run the rest of the suite; the forge runs the full check on the push.

Not done

• Gating each member singly: the queue already does this by leave-one-out and its re-gate, so I did not duplicate it. This pull records and classes the "no single culprit" case instead.
• Interaction red: a red that only appears when pulls are combined is still recorded as recheck and never held. It is held only if it reproduces on the pull alone.

To try it, run bun test test/doctor-culprit.test.ts.

Closes #11262

I addressed points 2–4, and for point 1 I'm narrowing the issue's scope instead of adding a new singly step. The type check passes, and test/doctor-culprit.test.ts and test/merge-queue.test.ts pass (29 tests). The gate script printed no output and the push went through.

What this pull does: when the queue narrows a red batch to one pull that is red only on top of pulls that landed first, the doctor classes the red. It records a recheck row with batch base:head+#a,#b and holds nothing. The recorded row is an audit trail, not the fix.

What changed this round

• Point 1, singly re-gate: I did not add a new step because the queue already does it. A red that neither side has moved off is gated again alone after REGATE_RED_MS (30 minutes, #3155), the regateDue path in src/crew/autonomy.ts. A reproduced red is held by treatRed, and one that goes green lands. That path serves #6534, and test/merge-queue.test.ts covers it ("gated once more after 30 minutes…"). If you want a different singly step, such as re-gating each member immediately with no wait, that is a separate change. I'd file it as its own issue. docs/features/batch-doctor.md now says this pull records and does not re-gate.
• Point 2, cap: noteRed in src/checks/doctor.ts now writes at most one recheck row per (pull, head, members). A flapping batch adds one row and no more. I did not exempt these rows from the 200 cap, so many different pulls can still fill it.
• Point 3, tests:

- The merge-queue test (test/merge-queue.test.ts) now drives the real queue and asserts the exact batch string, ^[0-9a-f]{12}:<head12>\+#a,#b$. After the re-gate wait, a second sweep adds no recheck row. - The reproduced-red test asserts the doctor's held row is the only row. - test/doctor-culprit.test.ts covers dedupe: same head and members is one row, different members is a second row.

• Point 4, docs: docs/features/batch-doctor.md says these rows are one per (pull, head, members) and share the 200 cap.

To try it: run bun test test/doctor-culprit.test.ts test/merge-queue.test.ts.