fix(01-02): replace Node EventEmitter with browser-compatible implementation

Node's 'events' module doesn't work in browsers. Replaced with custom
Map-based implementation that provides the same API but works in both
Node.js and browser environments.

All 98 tests still pass.

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

src/game/EventEmitter.ts

@@ -1,13 +1,11 @@
-// src/game/EventEmitter.ts - Typed event emitter wrapper
+// src/game/EventEmitter.ts - Typed event emitter (browser-compatible)
 /**
- * TypedEventEmitter provides a type-safe wrapper around Node's EventEmitter.
- * It ensures event names and payloads are correctly typed.
+ * TypedEventEmitter provides a type-safe event system that works in browsers.
+ * Custom implementation - no Node.js dependencies.
  */
 
-import { EventEmitter } from 'events';
-
 export class TypedEventEmitter<T extends object> {
-  private emitter = new EventEmitter();
+  private listeners = new Map<keyof T, Set<(data: T[keyof T]) => void>>();
 
   /**
    * Register a listener for an event
@@ -16,7 +14,10 @@ export class TypedEventEmitter<T extends object> {
    * @returns this for chaining
    */
   on<K extends keyof T>(event: K, listener: (data: T[K]) => void): this {
-    this.emitter.on(event as string, listener);
+    if (!this.listeners.has(event)) {
+      this.listeners.set(event, new Set());
+    }
+    this.listeners.get(event)!.add(listener as (data: T[keyof T]) => void);
     return this;
   }
 
@@ -27,8 +28,11 @@ export class TypedEventEmitter<T extends object> {
    * @returns this for chaining
    */
   once<K extends keyof T>(event: K, listener: (data: T[K]) => void): this {
-    this.emitter.once(event as string, listener);
-    return this;
+    const onceWrapper = (data: T[K]) => {
+      this.off(event, onceWrapper);
+      listener(data);
+    };
+    return this.on(event, onceWrapper);
   }
 
   /**
@@ -38,7 +42,12 @@ export class TypedEventEmitter<T extends object> {
    * @returns true if listeners were called, false otherwise
    */
   emit<K extends keyof T>(event: K, data: T[K]): boolean {
-    return this.emitter.emit(event as string, data);
+    const eventListeners = this.listeners.get(event);
+    if (!eventListeners || eventListeners.size === 0) {
+      return false;
+    }
+    eventListeners.forEach(listener => listener(data as T[keyof T]));
+    return true;
   }
 
   /**
@@ -48,7 +57,10 @@ export class TypedEventEmitter<T extends object> {
    * @returns this for chaining
    */
   off<K extends keyof T>(event: K, listener: (data: T[K]) => void): this {
-    this.emitter.off(event as string, listener);
+    const eventListeners = this.listeners.get(event);
+    if (eventListeners) {
+      eventListeners.delete(listener as (data: T[keyof T]) => void);
+    }
     return this;
   }
 
@@ -58,7 +70,7 @@ export class TypedEventEmitter<T extends object> {
    * @returns this for chaining
    */
   removeAllListeners<K extends keyof T>(event: K): this {
-    this.emitter.removeAllListeners(event as string);
+    this.listeners.delete(event);
     return this;
   }
 }