- Add @spec to AgentSocket callbacks (connect/3, id/1)
- Add @spec to AgentChannel callbacks (join/3, handle_info/2, handle_in/3)
- Add @spec to AgentChannel private function build_jobs_for_agent/1
- Add @spec to Agents.verify_agent_token/1
- Add @spec to Agents.update_agent_token_heartbeat/3
- Add @spec to Agents.list_agent_polling_targets/1
These specs provide strict type checking for the critical WebSocket
agent communication code implemented in this session.