feat(lotus): io.lotus.set_deafen action — deafen remote audio at the source

New toWidget action { deafened, screenshareAudioMuted } that sets each remote
RemoteParticipant.setVolume per source (Microphone + ScreenShareAudio), applied
to existing participants + re-applied to late joiners via
RoomEvent.ParticipantConnected (subscribed through vm.livekitRoomItems$). Closure-
scoped state, matching the sibling lotus modules; the cinny host re-sends on join
so a fresh call never inherits stale deafen state.

Replaces cinny's brittle iframe-DOM <audio>.muted hack (which broke on EC
re-render / late tracks). Folded into unpublished 0.20.1-lotus.2.

Note: injected/soundboard audio (Track.Source.Unknown) is not silenced — the
livekit-client setVolume type only accepts Microphone|ScreenShareAudio.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/room/InCallView.tsx

@@ -35,6 +35,7 @@ import { startLotusAudioInject } from "../lotus/lotusAudioInject";
 import { startLotusQuality } from "../lotus/lotusQuality";
 import { startLotusDecorations } from "../lotus/lotusDecorations";
 import { startLotusDenoise } from "../lotus/lotusDenoise";
+import { startLotusDeafen } from "../lotus/lotusDeafen";
 import styles from "./InCallView.module.css";
 import { GridTile } from "../tile/GridTile";
 import { SettingsModal, defaultSettingsTab } from "../settings/SettingsModal";
@@ -303,6 +304,10 @@ export const InCallView: FC<InCallViewProps> = ({
   // [lotus] Apply ML denoise to the mic as a first-class audio processor that
   // survives reconnects (#1 / A7). No-op unless lotusDenoiseSource=1.
   useEffect(() => startLotusDenoise(vm), [vm]);
+  // [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]);
 
   const fatalCallError = useBehavior(vm.fatalError$);
   // Stop the rendering and throw for the error boundary