Start or stop an EC2 instance by short host name while keeping the local host registry in sync through the UDP daemon on 127.0.0.1:5.
awsctl.py <start|stop> <host> [profile]
1. Ask the UDP daemon for the canonical instance id with canon <host>.
2. Use boto3 to start or stop that instance, optionally through a named AWS profile.
3. Wait for instance_running or instance_stopped before continuing.
4. On start, fetch the public IP and send host <instance_id> <ip>; on stop, send disable <instance_id>.
5. Finish with save so the daemon writes the updated hosts state.
This script assumes the daemon can translate host names to instance ids and persists the local hosts mapping. If AWS says an instance id no longer exists, the daemon or hosts state is stale.