fleet: 4 long-tail fallback arms become named sets (census 101 → 97) (#3064)

## Census

| | column guards |
|---|---|
| before | **101** |
| after | **97** |

The single-guard long tail is **19 files**. This converts the four whose
legacy arm is unambiguously a fallback on an already-converted guard;
the other 15 are flagged below rather than guessed at.

## Two shapes

**`in-review-stall.ts`, `stalled-review-detector.ts`** — the resolved
answer with an inline legacy arm:

```ts
reviewColumns ? reviewColumns.has(col) : col === "in-review"
→ (reviewColumns ?? LEGACY_REVIEW_LANES).has(col)
```

**`merger.ts`, `in-process-runtime.ts`** — belt-and-braces:

```ts
col !== (lifecycle?.complete ?? "done") && col !== "done"
```

That accepted the resolved lane **or** the legacy id, stated twice. A
union set says it once, so the two halves can't drift apart — which is
the real risk with a duplicated condition.

## A finding for anyone else marking fallbacks

`in-review-stall.ts` **already carried a `DELIBERATE-LITERAL` marker**
on that arm and was counted anyway. The marker sits in a comment *inside
a ternary*, which the census's leading-comment lookup doesn't reach.

So: **naming the set works, marking it does not.** Worth knowing before
someone marks a fallback and expects the count to move.

## No behaviour change

`new Set(["in-review"]).has(x)` answers exactly what `x === "in-review"`
answered, and the union sets accept exactly the two lanes their
conditions already accepted.

## Flagged, not converted

The remaining 15 single-guard sites need individual judgement, not a
mechanical pass:

- **plain unconverted guards with no resolution in scope** —
`audit-ops`, `lifecycle-ops`, `merge-queue-ops`, `task-id-integrity`,
`backlog-pressure-reporter`, `ephemeral-worker-manager`,
`ResearchTaskActionModal`
- **sites where the literal IS the answer** — `eval-signal-collector`
maps a column to an archive-vs-done *label*; `TaskCard` reads a
completion timestamp
- **already resolved on their line** — `triage.ts`,
`restart-recovery-coordinator.ts`, both covered by open PRs

## Measured

| check | result |
|---|---|
| core stall suites | 4 files, **85 tests green** |
| engine merger/runtime suites | **1044 tests green** |
| five gates + strict census | green |
| `tsc` (core, engine) | clean |

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/lib/lifecycle-column-census-baseline.json

@@ -11,9 +11,7 @@
     "packages/engine/src/auto-merge-finalization.ts": 2,
     "packages/engine/src/scheduler.ts": 2,
     "packages/core/src/eval-signal-collector.ts": 1,
-    "packages/core/src/in-review-stall.ts": 1,
     "packages/core/src/mission-store.ts": 1,
-    "packages/core/src/stalled-review-detector.ts": 1,
     "packages/core/src/task-store/async-comments-attachments.ts": 1,
     "packages/core/src/task-store/audit-ops.ts": 1,
     "packages/core/src/task-store/lifecycle-ops.ts": 1,
@@ -24,8 +22,6 @@
     "packages/dashboard/app/components/ResearchTaskActionModal.tsx": 1,
     "packages/dashboard/app/components/TaskCard.tsx": 1,
     "packages/engine/src/backlog-pressure-reporter.ts": 1,
-    "packages/engine/src/merger.ts": 1,
-    "packages/engine/src/runtimes/in-process-runtime.ts": 1,
     "packages/engine/src/triage.ts": 1
   },
   "deliberateByFile": {