feat(calls): audio output quick-switch in the call bar (#119)

Verified first: the embed hides Element Call's footer, so its in-call
settings sheet (which has the output picker) is unreachable from Lotus;
the cinny call bar had no output control.

Now a speaker button next to Deafen (desktop bar only; hidden where
setSinkId is unavailable — Firefox, Safari, Android Chrome) opens a menu
of enumerateDevices() audio outputs with the current one checked; picking
one sends io.lotus.set_audio_output to the fork (≥ 0.25.0-lotus.11),
which selects it, and the choice is re-sent with the rest of the sticky
fork state after an EC remount.

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

src/app/plugins/call/CallControl.ts

@@ -191,6 +191,7 @@ export class CallControl extends EventEmitter implements CallControlState {
   public resendForkState(): void {
     this.sendDeafenState();
     this.sendQuality();
+    if (this._audioOutputId !== undefined) this.sendAudioOutput(this._audioOutputId);
     // [Gitea #17] The pin lives fork-side and is dropped on a handler remount.
     if (this._focusedUserId !== null) this.sendFocus(this._focusedUserId, this._focusedMediaId);
   }
@@ -277,6 +278,24 @@ export class CallControl extends EventEmitter implements CallControlState {
   // P6-2: send deafen state to the fork (io.lotus.set_deafen). Join-gated: the
   // fork's handler only exists once joined; onCallJoined() re-sends the current
   // state so a pre-join deafen is not lost.
+  // [Gitea #119] Output device (headset ↔ speakers) chosen from the host's
+  // call bar; the fork applies it with mediaDevices.audioOutput.select().
+  private _audioOutputId: string | undefined;
+
+  public get audioOutputId(): string | undefined {
+    return this._audioOutputId;
+  }
+
+  public setAudioOutput(deviceId: string): void {
+    this._audioOutputId = deviceId;
+    this.sendAudioOutput(deviceId);
+  }
+
+  private sendAudioOutput(deviceId: string): void {
+    if (!this.joined) return;
+    this.call.transport.send('io.lotus.set_audio_output', { deviceId }).catch(() => undefined);
+  }
+
   private sendDeafenState(): void {
     if (!this.joined) return;
     this.call.transport