feat: add spawnNpc method to SocketClient

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/src/network/SocketClient.ts

@@ -45,6 +45,10 @@ export class SocketClient {
     this.socket.emit('player-input', input);
   }
 
+  spawnNpc(x: number, y: number): void {
+    this.socket.emit('spawn-npc', { x, y });
+  }
+
   disconnect(): void {
     this.socket.disconnect();
   }