Swarm ignores docker-compose.yaml's build: key, so docker stack deploy
previously needed an operator to build and tag the control-plane image
by hand. CI now publishes it to this instance's container registry on
every push to master (or a tag), and docker-compose.yaml's image: key
(overridable via GATEWAY_CONTROL_PLANE_IMAGE) lets Swarm pull it directly.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0142mP6EqCkQKmR1xCp7zfmZ
