Many upstream plugins publish no tags at all, so a tag-only installer cannot
manage them.
- Add a branch spec field, mutually exclusive with tag and validated the same way
- Build archive/refs/heads/<branch> URLs for branch specs
- Refetch a branch only on :ArtiPackUpdate or a forced sync, never from cache
- Record the branch, archive digest and fetch time in the lockfile
- Report a branch plugin as tracked and fetched, never as up to date
- add lua modules for spec parsing, lock state, fs helpers and the installer
- add ArtiPackSync/ArtiPackClean/ArtiPackList commands and help doc
- add headless nvim test harness and specs
- add make test/lint/fmt/pre-commit and patch/minor/major bump targets
- add woodpecker test, lint and pre-commit pipelines
unkin-agent