fix: 跨端消息同步 — 用户消息广播 + 会话隔离 + 去重

后端: handleChatMessage 将用户消息通过 broadcastToUser 广播给同用户所有设备
协议: ClientMessage 新增 ClientMsgID 字段用于跨端去重
前端: 发送消息时携带 client_msg_id，收到回显时跳过本地已添加的消息
前端: handleServerMessage 新增 session_id 过滤，防止不同会话消息串扰

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/gateway/internal/handler/chat_handler.go

@@ -168,8 +168,12 @@ func (h *ChatHandler) handleChatMessage(client *ws.Client, msg ws.ClientMessage)
 	}
 
 	// 缓存用户消息（在 goroutine 前完成，避免竞态）
+	userMsgID := msg.ClientMsgID
+	if userMsgID == "" {
+		userMsgID = "msg_" + generateID()
+	}
 	userMsg := ws.Message{
-		ID:        "msg_" + generateID(),
+		ID:        userMsgID,
 		Role:      "user",
 		Content:   msg.Content,
 		Timestamp: time.Now().UnixMilli(),
@@ -183,6 +187,21 @@ func (h *ChatHandler) handleChatMessage(client *ws.Client, msg ws.ClientMessage)
 	}
 	h.hub.CacheMessage(client.UserID, client.SessionID, userMsg)
 
+	// 广播用户消息给同用户所有设备（跨端同步）
+	h.broadcastToUser(client.UserID, ws.ServerMessage{
+		Type:      "response",
+		MessageID: userMsgID,
+		Content:   msg.Content,
+		Role:      "user",
+		MsgType:   "chat",
+		SessionID: client.SessionID,
+		Timestamp: time.Now().UnixMilli(),
+		ClientInfo: &ws.ClientInfo{
+			ClientID:   client.ClientID,
+			DeviceName: client.DeviceName,
+		},
+	})
+
 	// 在 goroutine 中进行 AI-Core 调用和流式发送，避免阻塞 ReadPump
 	go h.streamResponse(client, mode, reqBody, msg.Content)
 }

backend/gateway/internal/ws/protocol.go

@@ -24,6 +24,7 @@ type ClientMessage struct {
 	ClientID    string               `json:"client_id,omitempty"`    // 客户端唯一标识 (多端区分)
 	DeviceName  string               `json:"device_name,omitempty"`  // 设备备注名称
 	UserAgent   string               `json:"user_agent,omitempty"`   // 浏览器 UA
+	ClientMsgID string               `json:"client_msg_id,omitempty"` // 客户端消息ID (跨端去重)
 }
 
 // ReviewMessage 审查后的结构化消息（动作/聊天分离）

frontend/web/src/hooks/useChat.ts

@@ -37,6 +37,7 @@ export function useChat() {
         mode,
         attachments,
         timestamp: Date.now(),
+        client_msg_id: userMsgId,
       });
     },
     [addMessage, setTyping, sendMessage]

frontend/web/src/hooks/useWebSocket.ts

@@ -32,6 +32,28 @@ function getBackoffDelay(attempt: number): number {
 
 let wsInstanceCounter = 0;
 
+// ========== 跨端消息去重 ==========
+const sentMsgIds = new Set<string>();
+const MAX_SENT_IDS = 40;
+
+function trackSentMsgId(id: string) {
+  sentMsgIds.add(id);
+  if (sentMsgIds.size > MAX_SENT_IDS) {
+    const entries = [...sentMsgIds];
+    sentMsgIds.clear();
+    for (const entry of entries.slice(-MAX_SENT_IDS / 2)) {
+      sentMsgIds.add(entry);
+    }
+  }
+}
+
+// 会话作用域的消息类型：仅处理匹配当前会话的消息
+const SESSION_SCOPED_TYPES = new Set([
+  'response', 'stream_start', 'stream_chunk', 'stream_end',
+  'stream_segments', 'review', 'multi_message', 'thinking',
+  'tool_progress', 'system_info',
+]);
+
 export function useWebSocket() {
   const [isConnected, setIsConnected] = useState(false);
   const [reconnectAttempts, setReconnectAttempts] = useState(0);
@@ -162,6 +184,10 @@ export function useWebSocket() {
 
   const sendMessage = useCallback((msg: WSClientMessage) => {
     const instanceId = instanceIdRef.current;
+    // 注册 client_msg_id 用于跨端回显去重
+    if (msg.client_msg_id) {
+      trackSentMsgId(msg.client_msg_id);
+    }
     if (wsRef.current?.readyState === WebSocket.OPEN) {
       const sessionID = useSessionStore.getState().currentSessionId;
       wsRef.current.send(
@@ -200,20 +226,32 @@ function handleServerMessage(msg: WSServerMessage) {
   const { setMessages } = useSessionStore.getState();
   const chatState = useChatStore.getState();
 
+  // 会话作用域消息：仅处理匹配当前会话的消息，避免跨会话串消息
+  if (SESSION_SCOPED_TYPES.has(msg.type) && msg.session_id) {
+    const currentSid = useSessionStore.getState().currentSessionId;
+    if (currentSid && msg.session_id !== currentSid) {
+      return;
+    }
+  }
+
   switch (msg.type) {
     case 'stream_start':
 	      setTyping(true);
 	      break;
 
     case 'response':
-      // 支持两种格式: 旧版 (text 字段) 和 审查消息版 (content + role + msg_type 字段)
       if (msg.text || msg.content) {
+        // 跨端用户消息去重：本端已本地添加，跳过服务端回显
+        if (msg.role === 'user' && msg.message_id && sentMsgIds.has(msg.message_id)) {
+          break;
+        }
         addMessage({
           id: msg.message_id || '',
           role: (msg.role as Message['role']) || 'assistant',
           content: (msg.text || msg.content) as string,
           timestamp: msg.timestamp,
           msgType: (msg.msg_type as MessageDisplayType) || undefined,
+          client_info: msg.client_info,
         });
       }
       setTyping(false);

frontend/web/src/types/chat.ts

@@ -112,6 +112,7 @@ export interface WSClientMessage {
   client_id?: string;
   device_name?: string;
   user_agent?: string;
+  client_msg_id?: string; // 客户端消息ID (跨端去重)
 }
 
 /** 通知类型 */