Two things were wrong, and the second actively misled.
The publish instructions described pushing to the Gitea registry by hand.
Publishing now runs on GitHub Actions to ghcr.io, because Cloudflare's
request-body cap returns 413 on a registry layer and our own runners cannot
build images (host mode, all capabilities dropped). The example tag had also
been mangled to "12.11.1-ci".
"Package visibility is PUBLIC, so the runner namespace pulls without a secret"
was false. The Gitea package is private — flux-config's kustomization says so
in as many words — and the runner Deployments have always carried a pull
secret. Reading that line led me to conclude the ghcr package would need no
credential; it does, and forgejo-runner-system now holds
github-registry-credentials for exactly that.
Verified with `docker build --check`: no warnings.
agent