Add streaming support and refactor Chat UI

- Add run_stream method to AgentCore for streaming output
- Add base_url parameter to LLM clients for OpenRouter support
- Add xbot module for new agent implementation
- Refactor Chat.vue into composable + components (ChatHeader, ChatMessage, ChatInput, ChatSidebar, ChatAgentSelector)
- Add ChatStream handler for SSE streaming in Go server
- Add UseXBot field to chat request

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

server/internal/handler/agent_handler.go

@@ -26,6 +26,7 @@ type ChatRequest struct {
 	Message   string `json:"message" binding:"required"`
 	SessionID string `json:"session_id"`
 	ModelID   string `json:"model_id"`
+	UseXBot   bool   `json:"use_xbot"`
 }
 
 // ChatResponse 对话响应
@@ -56,6 +57,7 @@ func (h *AgentHandler) Chat(c *gin.Context) {
 		UserID:    userID,
 		SessionID: req.SessionID,
 		ModelID:   req.ModelID,
+		UseXBot:   req.UseXBot,
 	}
 
 	result, err := h.agentService.Chat(pythonReq)
@@ -85,6 +87,30 @@ func (h *AgentHandler) Chat(c *gin.Context) {
 	})
 }
 
+// ChatStream 单智能体对话（流式输出）
+func (h *AgentHandler) ChatStream(c *gin.Context) {
+	var req ChatRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	// 获取用户 ID
+	userID := 1 // TODO: 从 c.Get("user_id") 获取
+
+	// 构建 SSE 流
+	c.Header("Content-Type", "text/event-stream")
+	c.Header("Cache-Control", "no-cache")
+	c.Header("Connection", "keep-alive")
+	c.Header("Access-Control-Allow-Origin", "*")
+
+	// 调用 Python 服务的流式端点
+	err := h.agentService.ChatStream(c, req.AgentID, req.Message, req.SessionID, req.ModelID, userID)
+	if err != nil && !c.IsAborted() {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+	}
+}
+
 // TeamChatRequest 多智能体群聊请求
 type TeamChatRequest struct {
 	SupervisorAgentID int      `json:"supervisor_agent_id" binding:"required"`