`source.config.ts` feeds `docs/reference/**/*.md` to fumadocs-mdx, whose default
schema requires a `title`. #12478 added `docs/reference/REMOVED_PROVIDERS.md`
with no frontmatter block at all, so every production build died with:
[MDX] invalid frontmatter in docs/reference/REMOVED_PROVIDERS.md:
- title: Invalid input: expected string, received undefined
That single missing block is what turns three release-green gates red at once —
`Package artifact (npm pack policy)` fails on the build, and both
`Tarball boot-smoke` and the packaged CLI checks are skipped for lack of a
valid `dist/`.
Fixes:
- add the frontmatter block, matching the convention of its sibling reference
docs (`title` / `version` / `lastUpdated`).
- add `check:docs-frontmatter`, wired into `check:docs-all`, so the next doc
added without a title fails in milliseconds instead of costing a full Next
build and a red release branch. The gate reads its globs from
`source.config.ts` rather than duplicating them, so a new docs directory
cannot silently escape the check.
Verified: the gate reports OK across all 122 compiled docs, fails (exit 1) when
the frontmatter is removed, and `npm run check:docs-all` passes.
Adds docs/reference/REMOVED_PROVIDERS.md (policy + register: puter #10210,
the keyless provider removed in #12440), links it from the docs index and
AGENTS.md's provider checklist, and adds a regression test that fails if any
registered id, alias or domain shows up again in the provider catalogs, the
executor map or the registry/executor sources.
Co-authored-by: Markus Hartung <diegosouzapw@users.noreply.github.com>
