fix: server logs an error on extra registration payload fields

Addresses #1 by logging registration with extra fields. It would be possible to ignore
extra fields, but for now it's better to silently fail to prevent spam registrations.

server/src/main.py

@@ -70,6 +70,9 @@ class Server:
 
             if not agent_id:
                 agent_id = self.register_agent(agent_info)
+                if not agent_id:
+                    logger.error(f"Failed to register agent from {addr}")
+                    return
                 logger.info(f"Agent {agent_id} registered from {addr}")
                 self.commands[agent_id] = f"set_id {agent_id}"
             else: