update clear msg bc anthropic needs at least 1 msg in chat call

Author: EdwardoSunny

tradingagents/agents/utils/agent_utils.py

@@ -24,7 +24,7 @@ def delete_messages(state):
         removal_operations = [RemoveMessage(id=m.id) for m in messages]
 
         # Add a minimal placeholder message
-        placeholder = HumanMessage(content="Continue analysis")
+        placeholder = HumanMessage(content="Continue")
 
         return {"messages": removal_operations + [placeholder]}