fix: pre-landing review round — 8 auto-fixes + 8 accepted findings hardened

The ship review army (4 specialists + red-team + checklist, 29 findings)
produced 8 mechanical auto-fixes and 11 decisions; the accepted set:

- win32 slug parity completed: lib/bin-context.ts gains the remote-first
  outermost walk + degraded-cache self-heal the bash side got this wave —
  the two implementations now agree on the stray-marker live-bug shape,
  pinned by shared fixtures (multi-specialist 9/10 finding).
- probe honors the plan's bounded-read decision: 256KB prefix, extraction
  semantics mirrored from parseTranscriptJsonl so probe/prepare can never
  diverge on the same file (>1MB transcript test).
- policy normalize parity: bash normalize() now matches canonicalizeRemote
  on .git/-trailing and uppercase-.GIT shapes (7-shape corpus pinned two
  ways) — a deny for those shapes could previously slip the transcript gate.
- session-update reclaim is TOCTOU-safe (atomic mv-aside on both branches).
- settings-hook: unparseable settings.json errors instead of being replaced
  with {}; ensure-event keys on (event, source) so matcher changes update
  in place — never zero or two registrations.
- dot-only slug guard at both parse sites (hostile 'url = ..' can't escape
  projects/); enqueue tmp-file janitor (1h TTL, inside the drain lock);
  brain-sync .migrating never clobbered; drop-queue/status count .migrating;
  snapshot -o warning correct + surfaced in diff mode; version-bump test
  order-dependence removed; uninstall clears the advance stamp.

Deferred with record: slug heal-probe cost sentinel (P3 TODO), FF_OK
conflation (noted, misdiagnosis-only).

270 pass / 0 fail across the 10 touched suites.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/brain-sync.test.ts

@@ -473,6 +473,32 @@ describe('gstack-brain-sync --discover-new', () => {
   });
 });
 
+// ---------------------------------------------------------------
+// Enqueue tmp janitor: a writer killed between its tmp write and the
+// atomic rename orphans a .tmp-* file forever (it never becomes a
+// record, nothing else touches it). The drain reaps ones older than
+// 1 hour, inside its lock; fresh ones (in-flight enqueues) survive.
+// ---------------------------------------------------------------
+describe('enqueue tmp janitor', () => {
+  test('an orphaned .tmp-* older than 1h is reaped on --once; a fresh one survives', () => {
+    run(['gstack-artifacts-init', '--remote', bareRemote]);
+    run(['gstack-config', 'set', 'artifacts_sync_mode', 'full']);
+    fs.mkdirSync(spoolDir(), { recursive: true });
+
+    const oldTmp = path.join(spoolDir(), '.tmp-99999-x1');
+    fs.writeFileSync(oldTmp, '{"file":"projects/p/learnings.jsonl"}\n');
+    const past = new Date(Date.now() - 2 * 3600 * 1000);
+    fs.utimesSync(oldTmp, past, past);
+
+    const freshTmp = path.join(spoolDir(), '.tmp-99999-x2');
+    fs.writeFileSync(freshTmp, '{"file":"projects/p/learnings.jsonl"}\n');
+
+    expect(run(['gstack-brain-sync', '--once']).status).toBe(0);
+    expect(fs.existsSync(oldTmp)).toBe(false);  // orphan reaped
+    expect(fs.existsSync(freshTmp)).toBe(true); // in-flight write untouched
+  });
+});
+
 // ---------------------------------------------------------------
 // #2549 queue integrity: classified drops, privacy retention,
 // surgical rewrite, unpushed-commit detector