Allow specifying which commit to tag and archive when cutting a release,
rather than always using HEAD. The commit ref flows through to both
git tag and create-archives.sh's git archive call. When not specified,
both default to HEAD as before.
Assisted-by: OpenCode (Claude Opus 4.6)
Add a `copr_build` job to build RPMs in COPR on every PR for
early packaging feedback. The create-archive action calls
`tools/create-archives.sh`, a new shared script that generates source
and vendor tarballs from the current tree. `release.py` is updated to
use the same script, deduplicating the archive creation logic.
While we're here, tweak the vendor-filterer invocation to match bootc
(add `--tier 2` and use `*-unknown-linux-gnu` glob).
Closes: #59
Assisted-by: Claude Opus 4.6
