lotus(#6): render decoration in MediaView; fix store lifecycle

Review found in-call tiles use MediaView->Avatar, not TileAvatar, so the
decoration never rendered in-call (CRITICAL). Move the overlay into
MediaView, gated on the avatar's own visibility (!(video && videoEnabled))
so it never floats over live video; revert the TileAvatar changes.
Also ref-count the io.lotus.decorations registration (one shared handler,
no double-reply) and stop clearing the map on teardown so a transient
remount doesn't drop decorations (HIGH/MED).

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

src/lotus/lotusDecorations.ts

@@ -47,34 +47,51 @@ function safeImageUrl(raw: unknown): string | null {
   }
 }
 
+// Ref-counted single registration: the decoration roster is app-wide (keyed by
+// userId), so multiple tile/InCallView mounts must share ONE handler — otherwise
+// each would reply to the same widget request (double-reply) and a transient
+// remount would tear it down.
+let registrations = 0;
+let unregister: (() => void) | null = null;
+
 /**
- * Register the `io.lotus.decorations` handler. No effect unless the host sends
- * the action. Returns a teardown function.
+ * Register the `io.lotus.decorations` handler (ref-counted). No effect unless
+ * the host sends the action. Returns a teardown function.
  */
 export function startLotusDecorations(): () => void {
   const w = widget;
   if (!w) return () => undefined;
 
-  const handler = (ev: CustomEvent<IWidgetApiRequest>): void => {
-    void w.api.transport.reply(ev.detail, {});
-    const data = ev.detail.data as
-      | { decorations?: Record<string, unknown> }
-      | undefined;
-    const next: Record<string, string> = {};
-    if (data?.decorations && typeof data.decorations === "object") {
-      for (const [userId, url] of Object.entries(data.decorations)) {
-        const safe = safeImageUrl(url);
-        if (safe) next[userId] = safe;
+  if (registrations === 0) {
+    const handler = (ev: CustomEvent<IWidgetApiRequest>): void => {
+      void w.api.transport.reply(ev.detail, {});
+      const data = ev.detail.data as
+        | { decorations?: Record<string, unknown> }
+        | undefined;
+      const next: Record<string, string> = {};
+      if (data?.decorations && typeof data.decorations === "object") {
+        for (const [userId, url] of Object.entries(data.decorations)) {
+          const safe = safeImageUrl(url);
+          if (safe) next[userId] = safe;
+        }
       }
-    }
-    decorations = next;
-    emit();
-  };
+      decorations = next;
+      emit();
+    };
+    w.lazyActions.on(LotusWidgetActions.Decorations, handler);
+    unregister = () =>
+      w.lazyActions.off(LotusWidgetActions.Decorations, handler);
+  }
+  registrations += 1;
 
-  w.lazyActions.on(LotusWidgetActions.Decorations, handler);
   return () => {
-    w.lazyActions.off(LotusWidgetActions.Decorations, handler);
-    decorations = {};
-    emit();
+    registrations -= 1;
+    if (registrations <= 0) {
+      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.
+    }
   };
 }