修改前端，支持 react_reasoning 自定义事件显示

frontend/src/components/chat_area.py

@@ -159,7 +159,39 @@ def _handle_ai_response():
                 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":
+            elif event_type == "react_reasoning":
+                # 处理我们自定义的推理事件（来自 react_reason_node, web_search, rag, 子图等）
+                step = event.get("step", 1)
+                action = event.get("action", "unknown")
+                confidence = event.get("confidence", 0)
+                reasoning = event.get("reasoning", "")
+                
+                # 根据 action 类型显示不同的图标
+                action_icon = "🤔"
+                if "web_search" in action:
+                    action_icon = "🌐"
+                elif "rag" in action or "retrieve" in action:
+                    action_icon = "📚"
+                elif "subgraph" in action:
+                    action_icon = "📦"
+                elif "DIRECT" in action:
+                    action_icon = "💬"
+                elif "ROUTE" in action:
+                    action_icon = "🔀"
+                elif "TOOL" in action:
+                    action_icon = "🔧"
+                
+                api_thought += f"\n\n{action_icon} **第 {step} 次推理**"
+                api_thought += f"\n   📋 动作: {action}"
+                if confidence > 0:
+                    api_thought += f"\n   📊 置信度: {confidence:.2f}"
+                if reasoning:
+                    api_thought += f"\n   💭 {reasoning}"
+                
+                display_thought = api_thought
+                thought_placeholder.info(f"**🤔 思考过程 (正在思考...)**\n\n{display_thought}▌")
+            
+            elif event_type == "intent_classified":
                 intent = event.get("intent", "unknown")
                 confidence = event.get("confidence", 0)
                 reasoning = event.get("reasoning", "")