Use SharedArrayBuffer tile state and ring buffer for worker updates

- Share GameMapImpl tile state between worker and main via SharedArrayBuffer
- Add SAB-backed tile update ring buffer to stream tile changes instead of postMessage payloads
- Wire shared state/ring through WorkerClient, Worker.worker, GameRunner, and ClientGameRunner
- Update GameView to skip updateTile when shared state is enabled and consume tile refs from the ring

src/core/worker/WorkerMessages.ts

@@ -37,6 +37,7 @@ export interface InitMessage extends BaseWorkerMessage {
   clientID: ClientID;
   sharedTileRingHeader?: SharedArrayBuffer;
   sharedTileRingData?: SharedArrayBuffer;
+  sharedStateBuffer?: SharedArrayBuffer;
 }
 
 export interface TurnMessage extends BaseWorkerMessage {