feat(lotus): io.lotus.set_audio_output — host-driven output device switch (#119)

The embed hides Element Call's footer, so its own output picker is out of
reach; the host's call bar now sends io.lotus.set_audio_output { deviceId }
and the fork applies it via mediaDevices.audioOutput.select(), answering
with io.lotus.audio_output_state { deviceId } on every change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/lotus/lotusActions.ts

@@ -52,6 +52,10 @@ export enum LotusWidgetActions {
    * disconnect or in-call teardown, whichever comes first.
    */
   CallSummary = "io.lotus.call_summary",
+  /** toWidget: select the audio output device `{ deviceId }` (#119). */
+  SetAudioOutput = "io.lotus.set_audio_output",
+  /** fromWidget: the currently selected output `{ deviceId }` (#119). */
+  AudioOutputState = "io.lotus.audio_output_state",
 }
 
 /** toWidget Lotus actions that must be allow-listed in `initializeWidget`. */
@@ -61,4 +65,5 @@ export const LOTUS_TO_WIDGET_ACTIONS: LotusWidgetActions[] = [
   LotusWidgetActions.SetQuality,
   LotusWidgetActions.Decorations,
   LotusWidgetActions.SetDeafen,
+  LotusWidgetActions.SetAudioOutput,
 ];