feat: 新增 react_reason 循环思考过程的流式显示

- 修改 react_nodes.py，在推理时保存推理过程到状态
- 修改 agent_service.py，检测并发送推理过程事件到前端
- 修改 chat_area.py，接收并显示推理过程
- 修改 useChat.ts，添加对推理过程事件的支持

frontend/src/components/chat_area.py

@@ -139,7 +139,26 @@ def _handle_ai_response():
             import logging
             logging.debug(f"[Frontend Stream] 收到事件: {event_type}, 完整内容: {repr(event)}")
             
-            # 1. 处理各种控制事件，显示到思考过程
+            # 1. 处理推理过程事件 - 这是新增的！
+            if event_type == "react_reasoning":
+                step = event.get("step", 1)
+                action = event.get("action", "unknown")
+                confidence = event.get("confidence", 0)
+                reasoning = event.get("reasoning", "")
+                
+                logging.info(f"[Frontend] 收到推理过程 #{step}: {action}")
+                
+                # 添加到思考过程
+                api_thought += f"\n\n🤔 **第 {step} 次推理**"
+                api_thought += f"\n   📋 决策: {action}"
+                api_thought += f"\n   📊 置信度: {confidence:.2f}"
+                if reasoning:
+                    api_thought += f"\n   💭 推理过程: {reasoning}"
+                
+                display_thought = api_thought
+                thought_placeholder.info(f"**🤔 思考过程 (正在思考...)**\n\n{display_thought}▌")
+            
+            # 2. 处理各种控制事件，显示到思考过程
             if event_type == "intent_classified":
                 intent = event.get("intent", "unknown")
                 confidence = event.get("confidence", 0)

frontend/src/components/useChat.ts

@@ -181,8 +181,20 @@ export function useChat() {
     try {
       for await (const event of apiClient.chatStream(text, threadId, model)) {
         switch (event.type) {
+          // 新增：处理推理过程事件
+          case "react_reasoning":
+            console.log(`🤔 收到推理过程 #${event.step}: ${event.action}`);
+            updateCurrentMessage({
+              reasoning: (currentMessageRef.current?.reasoning || "") + 
+                `\n\n🤔 **第 ${event.step} 次推理**` +
+                `\n   📋 决策: ${event.action}` +
+                `\n   📊 置信度: ${event.confidence.toFixed(2)}` +
+                (event.reasoning ? `\n   💭 推理过程: ${event.reasoning}` : "")
+            });
+            break;
+            
           // 新增：处理意图分类事件
-          case 'intent_classified':
+          case "intent_classified":
             console.log(`🧠 意图识别: ${event.intent} (置信度: ${event.confidence})`);
             setLastIntent({
               intent: event.intent,