DUNGEONS-33: clean shutdown locks and add optional Telegram 2048

Co-authored-by: multica-agent <github@multica.ai>

src/shutdown.js

@@ -0,0 +1,29 @@
+// Keep the store locked until writers finish, or until the process exits.
+export function installShutdown(store, drain, { timeout = 5000 } = {}) {
+  const release = () => {
+    try { store.close(); }
+    catch { console.error('Could not remove the access store lock. Check file permissions.'); process.exitCode = 1; }
+  };
+  process.once('exit', release);
+  let stopping;
+  const stop = () => {
+    if (stopping) return stopping;
+    const deadline = setTimeout(() => {
+      console.error('Shutdown timed out; exiting and releasing the access store lock.');
+      process.exit(1);
+    }, timeout).unref();
+    stopping = Promise.resolve().then(drain).catch(() => {
+      console.error('Gateway shutdown failed.');
+      // Do not unlock while unfinished jobs could still write to the store.
+      process.exit(1);
+    }).then(() => {
+      clearTimeout(deadline);
+      release();
+    });
+    return stopping;
+  };
+  // Keep handlers installed so repeated Ctrl+C cannot interrupt cleanup.
+  process.on('SIGINT', stop);
+  process.on('SIGTERM', stop);
+  return stop;
+}