Plan 3 fix: GA turn_detection auto-create_response + reset state on WS reconnect

GA Realtime API requires create_response:true and interrupt_response:true
inside turn_detection — without them the model never auto-generates a
reply after VAD detects speech_stopped, so the relay idles out at 30s
with no assistant audio. Add both.

Client side: when the /device WS drops (Coolify rolling deploy, etc.),
Session.run_forever reconnects but the StateMachine kept whatever state
it was in — usually LISTENING, which permanently disables the wakeword.
Add StateMachine.force_idle() and a Callbacks.on_disconnected() hook;
main.py wires it to force the state back to IDLE on every disconnect.
Also harden Session's fire-and-forget send_* helpers to swallow
ConnectionClosed instead of bubbling up as unhandled task exceptions.

client/main.py

@@ -107,6 +107,14 @@ def _make_callbacks(sm: StateMachine, playback: PlaybackWorker):
                 playback.enqueue_wav(SLEEP_WAV, "sleep")
             else:
                 playback.enqueue_done_marker("sleep")
+
+        def on_disconnected(self) -> None:
+            # The conversation is gone with the WS — reset to IDLE so the
+            # wakeword detector can re-arm. Any pending assistant audio left
+            # in the playback queue still drains, but we drop a "sleep" done
+            # marker only if we were mid-session.
+            _log.info("on_disconnected: forcing state to IDLE")
+            sm.force_idle()
     return _CB()