fix(lotus): Wave-1 audit fixes (EC1–EC6)

- EC1: lotusQuality — track + clearTimeout the 500ms settle re-apply per room
  (was leaking a timer that fired on torn-down rooms).
- EC2/EC3: lotusQuality + lotusAudioInject drive off vm.allConnections$ instead
  of the remote-gated livekitRoomItems$ (were no-ops when alone), matching
  lotusDenoise.
- EC4: lotusDecorations resets its roster to {} on teardown so a decoration from
  a previous call can't render on a shared user in the next one.
- EC5: hoisted a stable useSyncExternalStore subscribe fn (was re-subscribing
  every tile render).
- EC6: lotusFocus only sets the spotlight when the userId field is present
  (a partial payload no longer clears the pin).

tsc clean. Needs a republish to ship.

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

src/lotus/lotusDecorations.ts

@@ -26,15 +26,16 @@ function emit(): void {
   for (const l of listeners) l();
 }
 
+// Stable module-scope subscribe reference, so `useSyncExternalStore` doesn't
+// re-subscribe (add/remove the listener) on every render of a tile.
+function subscribe(cb: () => void): () => void {
+  listeners.add(cb);
+  return () => listeners.delete(cb);
+}
+
 /** Subscribe a tile avatar to its participant's decoration URL (or undefined). */
 export function useLotusDecoration(userId: string): string | undefined {
-  return useSyncExternalStore(
-    (cb) => {
-      listeners.add(cb);
-      return () => listeners.delete(cb);
-    },
-    () => decorations[userId],
-  );
+  return useSyncExternalStore(subscribe, () => decorations[userId]);
 }
 
 function safeImageUrl(raw: unknown): string | null {
@@ -94,8 +95,12 @@ export function startLotusDecorations(): () => void {
       registrations = 0;
       unregister?.();
       unregister = null;
-      // Intentionally keep the last decorations map: a transient remount must
-      // not drop decorations until the host next pushes an update.
+      // Reset the roster once the last registration goes away, so a decoration
+      // pushed in call A can't leak onto a shared user in call B before the
+      // host re-pushes. Notify listeners so any still-mounted tile drops the
+      // now-stale overlay via the render path.
+      decorations = {};
+      emit();
     }
   };
 }