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/MessageManager.ts

@@ -8,6 +8,7 @@
  * - 移除了 MessageStateManager 包装层
  * - 直接使用 zustand store
  * - 服务层移至 services/ 目录
+ * - 移除了 SubscriptionManager，改用 Zustand selector 进行响应式订阅
  */
 
 import type { ConversationResponse, MessageResponse, MessageSegment, UserDTO } from '../../types/dto';
@@ -24,7 +25,7 @@ import { MessageSyncService } from './services/MessageSyncService';
 import { WSMessageHandler } from './services/WSMessageHandler';
 
 // 导入 store
-import { useMessageStore, subscriptionManager, normalizeConversationId } from './store';
+import { useMessageStore, normalizeConversationId } from './store';
 
 // 重新导出类型，保持兼容性
 export type {
@@ -164,23 +165,12 @@ class MessageManager {
 
         this.wsHandler.setBootstrapping(false);
 
-        subscriptionManager.notifySubscribers({
-          type: 'conversations_updated',
-          payload: { conversations: this.getConversations() },
-          timestamp: Date.now(),
-        });
-
         if (useMessageStore.getState().currentConversationId) {
           await this.fetchMessages(useMessageStore.getState().currentConversationId!);
         }
       } catch (error) {
         console.error('[MessageManager] 初始化失败:', error);
         this.wsHandler.setBootstrapping(false);
-        subscriptionManager.notifySubscribers({
-          type: 'error',
-          payload: { error, context: 'initialize' },
-          timestamp: Date.now(),
-        });
       }
     })();
 
@@ -194,7 +184,6 @@ class MessageManager {
   destroy(): void {
     this.wsHandler.disconnect();
     useMessageStore.getState().reset();
-    subscriptionManager.clear();
     this.syncService.restartSources();
     this.readReceiptManager.reset();
     this.deduplication.reset();
@@ -339,18 +328,6 @@ class MessageManager {
     await this.initialize();
     this.setActiveConversation(normalizedId);
 
-    // 先下发当前内存快照
-    const snapshot = this.getMessages(normalizedId);
-    subscriptionManager.notifySubscribers({
-      type: 'messages_updated',
-      payload: {
-        conversationId: normalizedId,
-        messages: [...snapshot],
-        source: 'activation_snapshot',
-      },
-      timestamp: Date.now(),
-    });
-
     const existingTask = this.activatingConversationTasks.get(normalizedId);
     if (existingTask && !options?.forceSync) {
       await existingTask;
@@ -371,81 +348,14 @@ class MessageManager {
     }
   }
 
-  // ==================== 订阅机制 ====================
-
-  subscribe(subscriber: import('./types').MessageSubscriber): () => void {
-    const unsubscribe = subscriptionManager.subscribe(subscriber);
-
-    // 立即发送当前状态给新订阅者（与原始版本保持一致）
-    subscriber({
-      type: 'conversations_updated',
-      payload: { conversations: this.getConversations() },
-      timestamp: Date.now(),
-    });
-
-    const unreadCount = this.getUnreadCount();
-    subscriber({
-      type: 'unread_count_updated',
-      payload: {
-        totalUnreadCount: unreadCount.total,
-        systemUnreadCount: unreadCount.system,
-      },
-      timestamp: Date.now(),
-    });
-
-    subscriber({
-      type: 'connection_changed',
-      payload: { connected: this.isConnected() },
-      timestamp: Date.now(),
-    });
-
-    // 如果当前有活动会话，立即发送该会话的消息给新订阅者
-    const activeConversationId = this.getActiveConversation();
-    if (activeConversationId) {
-      const currentMessages = this.getMessages(activeConversationId);
-      if (currentMessages.length > 0) {
-        subscriber({
-          type: 'messages_updated',
-          payload: {
-            conversationId: activeConversationId,
-            messages: [...currentMessages],
-            source: 'initial_sync',
-          },
-          timestamp: Date.now(),
-        });
-      }
-    }
-
-    return unsubscribe;
-  }
-
-  subscribeToMessages(conversationId: string, callback: (messages: MessageResponse[]) => void): () => void {
-    return subscriptionManager.subscribe((event) => {
-      if (event.type === 'messages_updated' && event.payload.conversationId === conversationId) {
-        callback(event.payload.messages);
-      }
-    });
-  }
-
   // ==================== 其他方法 ====================
 
   canLoadMoreConversations(): boolean {
     return this.syncService.canLoadMoreConversations();
   }
 
-  invalidateCache(_type?: 'all' | 'list' | 'unread'): void {
-    // 兼容性方法，新架构不需要外部缓存
-  }
-
-  async requestConversationListRefresh(
-    source: string,
-    options?: { force?: boolean; allowDefer?: boolean }
-  ): Promise<void> {
-    const forceRefresh = options?.force ?? true;
-    const allowDefer = options?.allowDefer ?? true;
-    
-    if (allowDefer && this.shouldDeferConversationRefresh(source, forceRefresh)) {
-      // 延迟刷新逻辑在 syncService 中处理
+  async refreshConversations(forceRefresh: boolean, source: string): Promise<void> {
+    if (this.shouldDeferConversationRefresh(source, forceRefresh)) {
       return;
     }