feat(voice): on-demand PodMan voice test + Hermes notify + TTS tuning

Snapshot of in-progress voice work, committed to unblock concurrent edits: speakInRoom + POST voice-test endpoint, Test PodMan voice button (PodView/api), Hermes notify action + scripts/hermes-notify.mjs, agent exits on LiveKit disconnect for auto-restart, TTS playback tuning (subscriber-ready delay, preroll/tail silence, fallback line, microphone source), verify script updates.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/agent.ts

@@ -173,6 +173,12 @@ async function main() {
     await withTimeout(dispose(), SHUTDOWN_GRACE_MS);
     process.exit(0);
   };
+  room.on(RoomEvent.Disconnected, () => {
+    if (!shuttingDown) {
+      console.error('[agent] LiveKit disconnected; exiting so systemd restarts the worker');
+      process.exit(1);
+    }
+  });
   process.on('SIGINT', shutdown);
   process.on('SIGTERM', shutdown);
 }