feat(events,session): add React-friendly subscribe APIs and snapshot getters

Adds backwards-compatible primitives needed to consume the renderer from
React 19 hooks (useSyncExternalStore, use(), TanStack Query) without
re-architecting the event bus.

- EventDispatcher.subscribe(type, cb): () => void — unsubscriber-returning
  wrapper matching the useSyncExternalStore subscribe signature.
- CommunicationManager.subscribeMessage(eventCtor, handler): () => void —
  packet-stream equivalent.
- SessionDataManager.getUserDataSnapshot() and
  RoomSessionManager.getActiveRoomSessionSnapshot() — referentially-stable
  read-only views invalidated through new SESSION_DATA_UPDATED and
  ROOM_SESSION_UPDATED events.

All additive; existing addEventListener/removeEventListener / IRoomSession
APIs are unchanged. Bumps renderer to 2.1.0.

packages/events/src/EventDispatcher.ts

@@ -101,4 +101,23 @@ export class EventDispatcher implements IEventDispatcher
     {
         this._listeners.clear();
     }
+
+    public subscribe<T extends INitroEvent>(type: string | string[], callback: (event: T) => void): () => void
+    {
+        if(!type || !callback) return () => {};
+
+        if(Array.isArray(type))
+        {
+            for(const t of type) this.addEventListener<T>(t, callback);
+
+            return () =>
+            {
+                for(const t of type) this.removeEventListener(t, callback);
+            };
+        }
+
+        this.addEventListener<T>(type, callback);
+
+        return () => this.removeEventListener(type, callback);
+    }
 }

packages/events/src/NitroEventType.ts

@@ -17,4 +17,6 @@ export class NitroEventType
     public static readonly AVATAR_EFFECT_DOWNLOADED = 'AVATAR_EFFECT_DOWNLOADED';
     public static readonly AVATAR_EFFECT_LOADED = 'AVATAR_EFFECT_LOADED';
     public static readonly FURNITURE_DATA_LOADED = 'FURNITURE_DATA_LOADED';
+    public static readonly SESSION_DATA_UPDATED = 'SESSION_DATA_UPDATED';
+    public static readonly ROOM_SESSION_UPDATED = 'ROOM_SESSION_UPDATED';
 }