fix(lotus): screenshare-audio mute survives a re-share — mute via the renderer, not setVolume

"Mute Screenshare Audio" (io.lotus.set_deafen screenshareAudioMuted) used
RemoteParticipant.setVolume(0, ScreenShareAudio). EC's own createVolumeControls
writes volume 1 through the same setter the moment a new screenshare media item
resolves, so when the sharer stopped and re-shared (or a late joiner shared)
the audio came back at full volume while the host button still said
"Unmute Screenshare Audio". Reproduced on the local calls stack with two
headless clients: after a re-share the screen_share_audio element read vol=1.

Now the flag is a global behavior (muteScreenshareAudio$) that
LivekitRoomAudioRenderer turns into the `muted` prop of every
Track.Source.ScreenShareAudio element — the exact mechanism deafen already uses
(pub.setEnabled(false): the server stops sending). Verified via the
RemoteTrackPublication behind each <audio>: the re-published track (new sid)
mounts with enabled=false while muted and re-enables on unmute; deafen +
undeafen leaves it muted; teardown resets the flag so the next call starts
clean. Unit tests updated; renderer test asserts only ScreenShareAudio
elements get muted by the new prop.

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

src/room/InCallView.tsx

@@ -73,6 +73,7 @@ import { matrixRTCMode as matrixRTCModeSetting } from "../settings/settings";
 import { ReactionsReader } from "../reactions/ReactionsReader";
 import { LivekitRoomAudioRenderer } from "../livekit/MatrixAudioRenderer.tsx";
 import { muteAllAudio$ } from "../state/MuteAllAudioModel.ts";
+import { muteScreenshareAudio$ } from "../lotus/lotusScreenshareAudio";
 import { useMediaDevices } from "../MediaDevicesContext.ts";
 import { EarpieceOverlay } from "./EarpieceOverlay.tsx";
 import {
@@ -261,6 +262,8 @@ export const InCallView: FC<InCallViewProps> = ({
   const { showControls, header: headerStyle } = useUrlParams();
 
   const muteAllAudio = useBehavior(muteAllAudio$);
+  // [lotus] host-driven "Mute Screenshare Audio" (io.lotus.set_deafen).
+  const muteScreenshareAudio = useBehavior(muteScreenshareAudio$);
   const toggleAudio = useBehavior(muteStates.audio.toggle$);
   const toggleVideo = useBehavior(muteStates.video.toggle$);
   const setAudioEnabled = useBehavior(muteStates.audio.setEnabled$);
@@ -309,7 +312,7 @@ export const InCallView: FC<InCallViewProps> = ({
   // [lotus] Handle the host's io.lotus.set_deafen action to silence remote
   // audio (and optionally screenshare audio) at the LiveKit source. No-op
   // unless the host sends the action.
-  useEffect(() => startLotusDeafen(vm), [vm]);
+  useEffect(() => startLotusDeafen(), []);
 
   const fatalCallError = useBehavior(vm.fatalError$);
   // Stop the rendering and throw for the error boundary
@@ -657,6 +660,7 @@ export const InCallView: FC<InCallViewProps> = ({
           livekitRoom={livekitRoom}
           validIdentities={participants}
           muted={muteAllAudio}
+          screenshareAudioMuted={muteScreenshareAudio}
         />
       ))}
       {renderContent()}