close() stopped the asyncio loop without disconnecting first, leaving the
EventDispatcher._process_events() task and the serial transport pending
("Task was destroyed but it is pending!" / "Event loop is closed").
Now await MeshCore.disconnect() and let the transport's connection_lost
callback settle before stopping the loop, then join the thread.
Found by running the adapter against a live MeshCore-flashed Heltec V3.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
