Refactor Dockerfile into multi-stage virgin/full targets and introduce a single
flag-based image build script. Standardize image naming, remove redundant build
scripts, and update Makefile targets accordingly. CI workflows now build missing
virgin images and run root and user tests consistently across all supported
distributions.
https://chatgpt.com/share/693c29d9-9b28-800f-a549-5661c783d968
- Introduce a GitHub Actions matrix for `test-container` and `test-e2e`
to run against arch, debian, ubuntu, fedora, and centos
- Run unit and integration tests only in the Arch container by passing
`distro="arch"` via make in the corresponding workflows
- Replace the global DISTROS loop with a single `distro` variable in
the Makefile, defaulting to `arch`, and export it for all scripts
- Update build scripts (build-image, build-image-no-cache, build-image-missing)
to build images for the selected distro only
- Simplify test-container script to validate a single distro image using
the `distro` environment variable
- Simplify E2E, unit, and integration test scripts to run against a
single distro container instead of iterating over all distros
https://chatgpt.com/share/693acbba-9e30-800f-94fb-fea4489e9078
