fix: improve error handling in buy/sell functions

Add proper exception handling around get_latest_position() calls in both
buy() and sell() functions. Previously, exceptions were caught but code
continued execution with undefined variables, causing "variable referenced
before assignment" errors.

Now returns error dict with context when position lookup fails.

Related to context injection implementation for concurrent simulations.

agent_tools/tool_trade.py

@@ -61,9 +61,7 @@ def buy(symbol: str, amount: int, signature: str = None, today_date: str = None)
     try:
         current_position, current_action_id = get_latest_position(today_date, signature)
     except Exception as e:
-        print(e)
+        return {"error": f"Failed to get position: {str(e)}", "signature": signature, "date": today_date}
-        print(current_position, current_action_id)
-        print(today_date, signature)
     # Step 3: Get stock opening price for the day
     # Use get_open_prices function to get the opening price of specified stock for the day
     # If stock symbol does not exist or price data is missing, KeyError exception will be raised
@@ -153,7 +151,10 @@ def sell(symbol: str, amount: int, signature: str = None, today_date: str = None
     # Step 2: Get current latest position and operation ID
     # get_latest_position returns two values: position dictionary and current maximum operation ID
     # This ID is used to ensure each operation has a unique identifier
-    current_position, current_action_id = get_latest_position(today_date, signature)
+    try:
+        current_position, current_action_id = get_latest_position(today_date, signature)
+    except Exception as e:
+        return {"error": f"Failed to get position: {str(e)}", "signature": signature, "date": today_date}
     
     # Step 3: Get stock opening price for the day
     # Use get_open_prices function to get the opening price of specified stock for the day