refactor(message): replace SubscriptionManager with Zustand selectors

Remove custom SubscriptionManager class and adopt Zustand's built-in
selector mechanism for reactive state updates. This simplifies the
architecture by eliminating manual subscription management and relying
on Zustand's automatic dependency tracking for component re-renders.

Key changes:
- Remove SubscriptionManager class from store.ts
- Replace all notifySubscribers calls with direct store updates
- Update hooks to use Zustand selectors with useShallow for complex data
- Remove subscribe/unsubscribe patterns from MessageManager
- Simplify EmbeddedChat to use selector instead of local state
- Rename requestConversationListRefresh to refreshConversations

src/stores/message/store.ts

@@ -1,11 +1,11 @@
 /**
  * 消息状态 Zustand Store
  * 使用 zustand 进行状态管理，提供响应式状态更新
- * 
+ *
  * 重构说明：
  * - 移除了 MessageStateManager 包装层
  * - 直接使用 zustand store 进行状态管理
- * - 订阅管理器集成到 store 中
+ * - 移除了 SubscriptionManager，改用 Zustand selector 进行响应式订阅
  */
 
 import { create } from 'zustand';
@@ -13,10 +13,6 @@ import type {
   ConversationResponse,
   MessageResponse,
 } from '../../types/dto';
-import type {
-  MessageSubscriber,
-  MessageEvent,
-} from './types';
 
 // ==================== 状态接口 ====================
 
@@ -377,52 +373,3 @@ export const useMessageStore = create<MessageStore>((set, get) => ({
   },
 }));
 
-// ==================== 订阅管理器 ====================
-
-/**
- * 订阅管理器类
- * 管理消息事件的订阅和通知
- */
-export class SubscriptionManager {
-  private subscribers: Set<MessageSubscriber> = new Set();
-
-  subscribe(subscriber: MessageSubscriber): () => void {
-    this.subscribers.add(subscriber);
-    return () => {
-      this.subscribers.delete(subscriber);
-    };
-  }
-
-  notifySubscribers(event: MessageEvent): void {
-    this.subscribers.forEach(subscriber => {
-      try {
-        subscriber(event);
-      } catch (error) {
-        console.error('[SubscriptionManager] 订阅者执行失败:', error);
-      }
-    });
-  }
-
-  clear(): void {
-    this.subscribers.clear();
-  }
-}
-
-// 创建全局订阅管理器实例
-export const subscriptionManager = new SubscriptionManager();
-
-// ==================== 便捷方法 ====================
-
-/**
- * 通知所有订阅者
- */
-export function notifySubscribers(event: MessageEvent): void {
-  subscriptionManager.notifySubscribers(event);
-}
-
-/**
- * 订阅消息事件
- */
-export function subscribeToMessages(subscriber: MessageSubscriber): () => void {
-  return subscriptionManager.subscribe(subscriber);
-}