Introduce `miaur self-update` / `--self-update` that clones RepoUrl@Branch,
detects user vs system install prefix, and reinstalls in place. Configurable
via conf/env; supports --noconfirm, --repo-url, and --branch.
Co-authored-by: Frank Vitrano <WHC2006@users.noreply.github.com>
Drop default --noconfirm (opt-in via --noconfirm), fix --noremovemake,
forward pacman argv intact for -R/-D/-F/-T/-U, deepen PKGBUILD review,
show an install plan before building, and add shellcheck CI plus unit tests.
Co-authored-by: Frank Vitrano <WHC2006@users.noreply.github.com>
