- helpers/paths.sh: validate_mirror/require_valid_mirror for the edge|rc|stable
set, and REPO_ROOT (OMARCHY_REPO_ROOT override) so a secondary checkout like
the rc branch worktree publishes into the same channel tree as the primary
- validate --mirror everywhere it previously accepted any string (sync-repo,
promote-build, update-repo, clean-repo, remove-package) and widen the
edge|stable checks in build, deploy, push-build, auto-release
- build/Dockerfile: rc builds compile against rc-mirror.omarchy.org
Ryan Hughes