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/gstack-slug-parity.test.ts

@@ -219,6 +219,20 @@ describe('gstack-slug ↔ remote-slug parity', () => {
     expect(fs.readFileSync(cacheFile, 'utf8').trim()).toBe('garrytan-gstack');
   });
 
+  test('hostile origin `url = ..` cannot become a ".." slug — basename fallback holds', () => {
+    // git accepts `..` as a remote URL; the sed parse passes it through
+    // unchanged, so unguarded it becomes SLUG=".." — filing state one level
+    // ABOVE ~/.gstack/projects/ (confined to ~/.gstack, but still traversal).
+    // The dot-only guard rejects it and the basename fallback anchors identity.
+    const repo = makeRepo(path.join(fixtures, 'dotty'), '..');
+    const r = runSlug(repo, tmpHome);
+    expect(r.status).toBe(0);
+    expect(slugOf(r)).toBe('dotty');
+    // The cache must hold the healed value, never the dot slug.
+    const cacheFile = path.join(tmpHome, '.gstack', 'slug-cache', encodedCacheKey(repo));
+    expect(fs.readFileSync(cacheFile, 'utf8').trim()).toBe('dotty');
+  });
+
   test('sticky identity preserved (#2212): repo that adopted a remote after first use is NOT healed', () => {
     // Legit sticky shape: the repo itself is the marker root (REMOTE_ROOT ==
     // PROJECT_ROOT) and its cached identity is its pre-origin basename slug.