tmu
3e33b51d1b
build:runner-image broke the script prefix convention: build is a bare single-tool command, and no tier fits a docker-daemon + registry-cred action, so the script leaves package.json and is invoked directly. CONTRIBUTING gains a 'CI runner image' section recording where the image pushes (gitea.e1nsnull.de/tmu/act-ci:<version>), the .node-version coupling, and the three-step Node-bump ritual.