feat: mute screenshare audio independently + fix CI lint/prettier

- Add screenshareAudioMuted state to CallControlState and CallControl
- setSound() now preserves screenshare audio mute when un-deafening
- Add toggleScreenshareAudio() targeting audio[data-lk-source="screen_share_audio"]
- Add ScreenshareAudioButton (volume icon, warns when muted) to controls bar
- Fix unused prevScreenshare variable (ESLint error from prior commit)
- Run Prettier on Controls.tsx and CallControl.ts (CI formatting failures)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/call/Controls.tsx

@@ -197,11 +197,41 @@ export function FullscreenButton({ isFullscreen, onToggle }: FullscreenButtonPro
           aria-pressed={isFullscreen}
           outlined
         >
-          {isFullscreen ? (
-            <ExitFullscreenIcon />
-          ) : (
-            <FullscreenIcon />
-          )}
+          {isFullscreen ? <ExitFullscreenIcon /> : <FullscreenIcon />}
+        </IconButton>
+      )}
+    </TooltipProvider>
+  );
+}
+
+type ScreenshareAudioButtonProps = {
+  muted: boolean;
+  onToggle: () => void;
+};
+export function ScreenshareAudioButton({ muted, onToggle }: ScreenshareAudioButtonProps) {
+  return (
+    <TooltipProvider
+      position="Top"
+      delay={500}
+      tooltip={
+        <Tooltip>
+          <Text size="T200">{muted ? 'Unmute Screenshare Audio' : 'Mute Screenshare Audio'}</Text>
+        </Tooltip>
+      }
+    >
+      {(anchorRef) => (
+        <IconButton
+          ref={anchorRef}
+          variant={muted ? 'Warning' : 'Surface'}
+          fill="Soft"
+          radii="400"
+          size="400"
+          onClick={onToggle}
+          aria-label={muted ? 'Unmute Screenshare Audio' : 'Mute Screenshare Audio'}
+          aria-pressed={muted}
+          outlined
+        >
+          <Icon size="400" src={muted ? Icons.VolumeMute : Icons.VolumeHigh} filled={muted} />
         </IconButton>
       )}
     </TooltipProvider>