Fix brainstorm server crashing on shutdown when the session dir is gone

skills/brainstorming/scripts/server.cjs

@@ -613,15 +613,26 @@ function startServer() {
   });
   watcher.on('error', (err) => console.error('fs.watch error:', err.message));
 
+  let shuttingDown = false;
   function shutdown(reason) {
+    if (shuttingDown) return;
+    shuttingDown = true;
     console.log(JSON.stringify({ type: 'server-stopped', reason }));
-    const infoFile = path.join(STATE_DIR, 'server-info');
-    if (fs.existsSync(infoFile)) fs.unlinkSync(infoFile);
-    fs.writeFileSync(
-      path.join(STATE_DIR, 'server-stopped'),
-      JSON.stringify({ reason, timestamp: Date.now() }) + '\n'
-    );
-    watcher.close();
+    // State-dir bookkeeping is best effort. The session directory can be removed
+    // while the server sits idle, and a missing or read-only state dir must never
+    // abort shutdown -- throwing here would skip every cleanup step below and kill
+    // the process with an uncaught exception instead of exiting 0.
+    try {
+      if (fs.existsSync(STATE_DIR)) {
+        const infoFile = path.join(STATE_DIR, 'server-info');
+        if (fs.existsSync(infoFile)) fs.unlinkSync(infoFile);
+        fs.writeFileSync(
+          path.join(STATE_DIR, 'server-stopped'),
+          JSON.stringify({ reason, timestamp: Date.now() }) + '\n'
+        );
+      }
+    } catch (e) { /* best effort */ }
+    try { watcher.close(); } catch (e) { /* content dir may be gone */ }
     clearInterval(lifecycleCheck);
     // Close any upgraded WebSocket sockets so server.close() can complete and
     // the process actually exits instead of lingering on an open connection.

tests/brainstorm-server/lifecycle.test.js

@@ -508,6 +508,27 @@ async function runTests() {
     assert(exited, 'idle shutdown must still fire despite a flood of unauthenticated requests');
   });
 
+  await test('idle shutdown exits 0 when the session dir was removed', async () => {
+    const dir = fs.mkdtempSync('/tmp/bs-life-');
+    const srv = spawn('node', [SERVER], { env: { ...process.env, BRAINSTORM_PORT: 3420, BRAINSTORM_DIR: dir, BRAINSTORM_IDLE_TIMEOUT_MS: 400, BRAINSTORM_LIFECYCLE_CHECK_MS: 100 } });
+    let out = ''; srv.stdout.on('data', d => out += d.toString());
+    let err = ''; srv.stderr.on('data', d => err += d.toString());
+    let code = null; srv.on('exit', c => { code = c; });
+    for (let i = 0; i < 60 && !out.includes('server-started'); i++) await sleep(50);
+
+    // The session dir can be cleaned up while the server sits idle. Shutdown
+    // bookkeeping is best effort: if writing state/server-stopped throws, the
+    // cleanup below it never runs and the process dies on an uncaught exception.
+    fs.rmSync(dir, { recursive: true, force: true });
+
+    for (let i = 0; i < 40 && code === null; i++) await sleep(100);
+    if (code === null) await killAndWait(srv);
+    fs.rmSync(dir, { recursive: true, force: true });
+
+    assert.strictEqual(code, 0, `idle shutdown must exit 0 with the session dir gone, got ${code}: ${err}`);
+    assert(!/ENOENT/.test(err), `shutdown must not throw ENOENT, got: ${err}`);
+  });
+
   console.log(`\n--- Results: ${passed} passed, ${failed} failed ---`);
   if (failed > 0) process.exit(1);
 }