The flake and its modules now own every config these files provided;
they remain in history for reference while the migration finishes.
BREAKING CHANGE: `.config/`, `.gitconfig`, and `.github/` no longer exist
at the repository root. A checkout that deploys this tree into `$HOME`
will delete the live configs it previously installed.
reference/ is a read-only snapshot of the pre-migration machine, kept
locally for porting configs but not part of the flake. Stop tracking it
and ignore it so migrations don't churn the repo.
