fix: defer AEC toggle until after screen picker resolves to prevent mic dropout

AudioManager.setScreenShareActive(true) was firing before the browser's screen
picker, killing the mic stream. The picker suspends getUserMedia while its secure
overlay is open, trapping the mic in a dead state for 5-30s. Now the AEC rebuild
fires after the track is acquired — mic stays alive during the picker.

packages/web/src/utils/screenShare.ts

@@ -70,11 +70,12 @@ export async function startScreenShare(room: Room): Promise<boolean> {
   const { videoQuality } = useVoiceStore.getState();
   const preset = SCREEN_QUALITY_MAP[videoQuality] || AUTO_PRESET;
 
-  // Notify AudioManager BEFORE enabling screen share so the mic track
-  // gets republished with AEC off, preventing Chrome's ducking.
-  AudioManager.getInstance().setScreenShareActive(true);
-
   try {
+    // NOTE: We do NOT call AudioManager.setScreenShareActive(true) before the
+    // browser picker. The picker suspends getUserMedia while its secure overlay
+    // is open — if we killed the mic stream here (to rebuild without AEC), the
+    // mic would stay dead until the user picks a screen (5-30s of silence).
+    // Instead we defer the AEC toggle to after the track is acquired.
     const track = await room.localParticipant.setScreenShareEnabled(true, {
       audio: true,
       resolution: preset.resolution,
@@ -88,10 +89,14 @@ export async function startScreenShare(room: Room): Promise<boolean> {
 
     if (!track) {
       // User cancelled the screen picker
-      AudioManager.getInstance().setScreenShareActive(false);
       return false;
     }
 
+    // NOW that the track is acquired and published, rebuild the mic without AEC.
+    // Chrome's AEC uses screen share audio as a reference signal and ducks the mic;
+    // this severs that link. The mic is dead for ~50ms during the rebuild — imperceptible.
+    AudioManager.getInstance().setScreenShareActive(true);
+
     // Tell the encoder to optimize for motion (more P-frames, fewer I-frames)
     // Must be set BEFORE the overdrive timer so the encoder knows from frame 1
     const screenPub = room.localParticipant.getTrackPublications()