fix: hide tool calls from chatbot history

modules/features/chatBot/service.py

@@ -561,13 +561,14 @@ async def get_thread_messages_from_langgraph(
         if msg.type not in ["human", "ai"]:
             continue
 
-        # Convert content to string if needed
-        content = msg.content if isinstance(msg.content, str) else str(msg.content)
+        # Skip messages with non-string content (e.g., tool calls)
+        if not isinstance(msg.content, str):
+            continue
 
         messages.append(
             {
                 "role": ROLE_MAP.get(msg.type, msg.type),
-                "content": content,
+                "content": msg.content,
             }
         )