`init` emits callers that say
`uses: grimoire-rs/indexer/.github/workflows/index-pages.yml@vX.Y.Z`, but
both reusable workflows only ever lived under `templates/reusable/`.
GitHub does not resolve a reusable workflow outside `.github/workflows/`,
so the first push to a scaffolded index failed at workflow resolution —
before any job existed, which is why the run had no log to show.

Move them to the path the callers name and cover the gap that let it
ship: the emitted refs are now resolved against this repo's working tree
and asserted to point at a file that exists, at this package's own tag.

The GitLab include was already correct — it names
`templates/reusable/gitlab-index-ci.yml`, which is in the tarball and the
repo — so that file stays put.