- Keep pre-build cleanup on GH runners (free-disk-space action and Docker builder/system prune) to prevent ENOSPC during builds.
- Remove post-job prune steps for both GH and ephemeral self-hosted runners since runners are discarded after the job and setup-buildx uses cleanup=true to remove builders automatically.
- Retain fallback: self-hosted build runs only if the GH build fails; publish succeeds if either path succeeds; final job fails only if both builds fail.
- Add “Free Disk Space (Ubuntu)” and Docker prune steps before/after the GitHub-hosted build to recover tens of GB and avoid “no space left on device” failures on ubuntu-latest.
- Remove continue-on-error and gate the self-hosted job with `always() && needs.build-gh.result != 'success'` so it runs only if the GH build fails, while publish proceeds if either path succeeds.
- Enable buildx GHA cache (cache-from/cache-to) to minimize runner disk pressure and rebuild times without loading images locally.
Replace job‑level continue‑on‑error with a step‑level setting and export build_succeeded from the docker/build‑push step to drive the fallback condition, guaranteeing the self‑hosted job runs whenever the GitHub runner fails (e.g., disk space) instead of being masked by a successful job conclusion. Update publish/finalize gating to rely on the explicit output flag (or self‑hosted success) so releases proceed only when at least one build path publishes successfully.
