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/cmd/api/main.go

@@ -333,11 +333,15 @@ func main() {
 
 	// 7. 设置路由
 	r := gin.New()
-
-	// 添加日志和恢复中间件
 	r.Use(gin.Logger())
 	r.Use(gin.Recovery())
 
+	// 禁用响应缓冲，用于流式输出
+	r.Use(func(c *gin.Context) {
+		c.Header("X-Accel-Buffering", "no")
+		c.Next()
+	})
+
 	// 请求日志中间件
 	r.Use(func(c *gin.Context) {
 		start := time.Now()
@@ -495,6 +499,7 @@ func main() {
 	agentGroup := r.Group("/api/agent")
 	{
 		agentGroup.POST("/chat", agentHandler.Chat)
+		agentGroup.POST("/chat/stream", agentHandler.ChatStream)
 		agentGroup.POST("/team/chat", agentHandler.TeamChat)
 	}