fix: use static template for logfire.info to avoid format string errors

Author: nikhilwoodruff

src/policyengine_api/agent_sandbox.py

@@ -390,7 +390,7 @@ def get_trace_headers() -> dict:
         return {}
 
     def log(msg: str) -> None:
-        logfire.info(msg, call_id=call_id)
+        logfire.info("agent_log", message=msg, call_id=call_id)
         print(msg)
         if call_id:
             try: