Reason: keep ci directory in sync
- https://github.com/NixOS/nixpkgs/pull/431450#issuecomment-3209546418
This requires that we have a modules directory, in which case the
easy and robust solution is to only port the addition parts of the refactor.
It's about as easy as a .keep file, but more useful.
This means that some duplication is created, but we avoid backporting the
changes to the documentation generation, which is a somewhat complex
component I'd rather not touch until these changes have been proven out
on unstable.
