fix: pre-landing review fixes — review-army findings hardened

Specialist review (testing, maintainability, security, performance,
data-migration) findings, each verified against code before fixing:

- legacy remove: preserve malformed/foreign entries (hooks absent, non-array,
  or pre-existing empty) — only entries THIS pass emptied are dropped
- add-event: never tag a mixed entry (old gstack versions in sibling
  worktrees treat tags as entry-level ownership and would destroy the user's
  co-located items); tag only single-item entries; prune-stale drops tags
  from mixed entries for the same reason
- prune-stale: within-entry twin collapse (two dead copies of one hook
  re-pointed to the same canonical command no longer double-fire); command
  quoting hardened via gsQuoteCmd (escapes \\ " $ backtick; gsStripWrap
  unescapes so identity round-trips); NUL bytes in the dedupe key replaced
  with a JSON.stringify key (bash silently dropped the NULs, degrading the
  separator; the file also read as binary to tooling)
- gsIsAlive: only provable absence (ENOENT/ENOTDIR) counts as dead —
  EACCES/EIO/unmounted volumes no longer prune (one-way-ratchet guard)
- gsWriteIfChanged: preserves the live settings.json mode across rewrites
  (a user-tightened 0600 carrying API keys was silently broadened to 0644);
  fresh files start 0600; backups rotate (keep 10)
- remove-source: command-less items default to foreign (gstack only writes
  type:command items); single-item stray claim requires a command
- rollback: pointer target must be a sibling settings.json.bak.* file
- uninstall + setup --no-team + SessionStart registration: stderr stays
  attached — a lock give-up or fail-closed parse during TEARDOWN must be
  visible ("the next setup retries" does not apply after uninstall)
- setup: team-mode banner no longer claims an auto-update hook when
  registration was skipped; heal log documents the rollback-pointer caveat;
  SESSION_UPDATE_CMD quoting mirrors gsQuoteCmd; lock constants named
- list-sources: corrupt settings.json reports to stderr instead of silently
  printing nothing (setup guards must not misread corrupt as no-hooks)
- tests: 10 new pins (malformed-entry preservation, mixed no-tag, twin
  collapse, 0600 mode, metachar escaping round-trip, backup rotation,
  rollback pointer refusal, held-lock uninstall warning, matcher-drift
  tripwire, ownership negatives)

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

test/uninstall.test.ts

@@ -298,3 +298,54 @@ describe('hook cleanup runs before the install root is deleted', () => {
     }
   });
 });
+
+describe('hook cleanup under lock contention is loud, never silent (review-army)', () => {
+  test('a held foreign lock during uninstall surfaces the give-up warning on stderr', () => {
+    const tmp = fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-uninstall-lock-'));
+    try {
+      const mockHome = path.join(tmp, 'home');
+      const installRoot = path.join(mockHome, '.claude', 'skills', 'gstack');
+      const installBin = path.join(installRoot, 'bin');
+      fs.mkdirSync(installBin, { recursive: true });
+      for (const b of ['gstack-uninstall', 'gstack-settings-hook', 'gstack-session-update', 'gstack-config']) {
+        const dst = path.join(installBin, b);
+        fs.copyFileSync(path.join(ROOT, 'bin', b), dst);
+        fs.chmodSync(dst, 0o755);
+      }
+      const settingsFile = path.join(mockHome, '.claude', 'settings.json');
+      fs.writeFileSync(settingsFile, JSON.stringify({
+        hooks: {
+          Stop: [{
+            _gstack_source: 'gstack-timeline-stop',
+            hooks: [{ type: 'command', command: `${installRoot}/hosts/claude/hooks/timeline-stop-hook` }],
+          }],
+        },
+      }, null, 2));
+      fs.mkdirSync(path.join(mockHome, '.gstack'), { recursive: true });
+      // A fresh foreign lock: pre-fix, every cleanup call silently skipped and
+      // uninstall reported clean while orphaning the hooks forever.
+      fs.mkdirSync(`${settingsFile}.lock`);
+      fs.writeFileSync(path.join(`${settingsFile}.lock`, 'owner'), 'another-live-process');
+
+      const result = spawnSync('bash', [path.join(installBin, 'gstack-uninstall'), '--force', '--keep-state'], {
+        stdio: 'pipe',
+        env: {
+          ...process.env,
+          HOME: mockHome,
+          GSTACK_SETTINGS_FILE: settingsFile,
+          GSTACK_STATE_ROOT: path.join(mockHome, '.gstack'),
+          GSTACK_SETTINGS_LOCK_TIMEOUT_MS: '300',
+        },
+        cwd: tmp,
+      });
+      const stderr = result.stderr.toString();
+      const s = JSON.parse(fs.readFileSync(settingsFile, 'utf-8'));
+      const cleaned = s.hooks?.Stop === undefined;
+      // Either the sweep still happened, or the user SEES why it didn't.
+      expect(cleaned || /could not acquire lock/.test(stderr)).toBe(true);
+      expect(/could not acquire lock/.test(stderr)).toBe(true);
+    } finally {
+      fs.rmSync(tmp, { recursive: true, force: true });
+    }
+  });
+});