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/api/src/nitro/session/IRoomSessionSnapshot.ts

@@ -0,0 +1,18 @@
+import { IRoomSession } from './IRoomSession';
+
+export interface IRoomSessionSnapshot
+{
+    roomId: number;
+    state: string;
+    isRoomOwner: boolean;
+    isSpectator: boolean;
+    isDecorating: boolean;
+    isGuildRoom: boolean;
+    isPrivateRoom: boolean;
+    controllerLevel: number;
+    doorMode: number;
+    tradeMode: number;
+    allowPets: boolean;
+    groupId: number;
+    session: IRoomSession;
+}