Turning ci/jenkins/docker-compose.yml from the controller into the agent meant
that redeploying a Jenkins set up from the old file would replace the
controller with an agent. Keep that file as the controller instead: the same
jenkins service and jenkins_home volume, now on the stock Java 25 image (its
old build context, ci/jenkins/Dockerfile, is the agent image now). The agent
moves to docker-compose.agent.yml. This replaces the previous commit's warning.
Alexa