feat: enhance agent orchestration, knowledge flow and UI refinements

backend/app/routers/conversation.py

@@ -1,4 +1,5 @@
 from fastapi import APIRouter, Depends, HTTPException, WebSocket, WebSocketDisconnect
+
 from fastapi.responses import StreamingResponse
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select, desc
@@ -92,13 +93,16 @@ async def chat(
 ):
     """简单版对话（非流式）"""
     agent_svc = AgentService(db)
-    conv_id, msg_id, content, model_name = await agent_svc.chat_simple(
-        user_id=current_user.id,
-        message=data.message,
-        conversation_id=data.conversation_id,
-        file_ids=data.file_ids,
-        model_name=data.model_name,
-    )
+    try:
+        conv_id, msg_id, content, model_name = await agent_svc.chat_simple(
+            user_id=current_user.id,
+            message=data.message,
+            conversation_id=data.conversation_id,
+            file_ids=data.file_ids,
+            model_name=data.model_name,
+        )
+    except ValueError as exc:
+        raise HTTPException(status_code=400, detail=str(exc))
 
     # 更新对话消息计数
     result = await db.execute(select(Conversation).where(Conversation.id == conv_id))
@@ -126,13 +130,17 @@ async def chat_stream(
     agent_svc = AgentService(db)
 
     async def stream_generator():
-        conv_id, msg_id, stream = await agent_svc.chat(
-            user_id=current_user.id,
-            message=data.message,
-            conversation_id=data.conversation_id,
-            file_ids=data.file_ids,
-            model_name=data.model_name,
-        )
+        try:
+            conv_id, msg_id, stream = await agent_svc.chat(
+                user_id=current_user.id,
+                message=data.message,
+                conversation_id=data.conversation_id,
+                file_ids=data.file_ids,
+                model_name=data.model_name,
+            )
+        except ValueError as exc:
+            yield f"event: error\ndata: {json.dumps({'error': str(exc)}, ensure_ascii=False)}\n\n"
+            return
 
         yield f"event: metadata\ndata: {json.dumps({'conversation_id': conv_id, 'message_id': msg_id})}\n\n"