Connect to server on mount via @work(thread=True). Bridge pymumble
callbacks to Textual messages (ServerConnected, ServerDisconnected,
TextMessageReceived, ServerStateChanged). Render live channel/user
tree recursively. Send text on input submit. Clean disconnect on quit.
Convert connect/disconnect to blocking calls (pymumble is synchronous).
Remove asyncio loop coupling. Add set_dispatcher() for marshalling
callbacks into the host event loop. Register all pymumble callbacks:
connected, disconnected, user/channel CRUD, text message, sound.
