`git mv` from src/ into plugins/ staged a rename, and a staged rename beats
.gitignore — so the platform repo committed a file belonging to a plugin that
owns its own repository. the file is unchanged on disk and is committed where
it belongs, in plugins/atelier.
worth knowing generally: moving a file OUT of a tracked directory into an
ignored one needs `git rm --cached` afterwards. the ignore rule does not undo
a rename that is already in the index.