act_runner-based deployment that handles `runs-on: silvermetal-builder` jobs.
Adapted from the stinky-roger-tv flutter-builder pattern with three changes:
- privileged: true (live-build needs loop devices + chroot)
- 4h job timeout (covers two reproducibility-gated ISO builds + diffoscope)
- silvermetal-builder label maps to catthehacker/ubuntu:act-latest, not the
silvermetal-builder image — the builder image stays minimal (no docker-cli),
and build.sh invokes it via `docker run` from the catthehacker job shell
Deployed at /opt/silvermetal-builder-runner/ on the SLAB docker host
(10.0.0.51); registered with git.silverlabs.uk and reporting healthy.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
