feat(gates): parse every docs frontmatter block locally, not in next build

.github/workflows/lint.yml

@@ -621,6 +621,41 @@ jobs:
  - name: Doc/skill authoring guard
  run: pnpm check:doc-authoring
 
+ # Docs frontmatter parses (#10493). Nothing local YAML-parsed these pages.
+ # The one gate that reads them line by line — `check:doc-anchors` below —
+ # deliberately BLANKS the frontmatter block ("preserving line count"),
+ # which is right for heading ids and left the closest thing to a
+ # frontmatter reader as the thing that erases it. So "every page's
+ # frontmatter parses" had exactly one owner: the `Build Docs` job in
+ # ci.yml, a full `next build` on a 30-minute-timeout runner that exists
+ # only in CI and is path-filtered besides. A page landed whose unquoted
+ # `description` contained `apis: `, YAML read the colon-plus-space as the
+ # start of a nested mapping, and that build was what said so.
+ #
+ # This reads the corpus with the docs build's OWN extractor regex and the
+ # same `yaml` parser fumadocs resolves, and types the two keys
+ # `pageSchema` declares (`title: z.string()` required,
+ # `description: z.string().optional()` typed when present) — not a schema
+ # of its own: the shape one character from the original defect PARSES and
+ # yields an object, and only the type assertion sees it.
+ #
+ # Population is the WHOLE corpus, generated `references/**` included,
+ # because that is what `Build Docs` parses; scoping to the hand-written
+ # half would leave 214 of 403 pages carrying the gap this closes. Every
+ # unread state is a refusal rather than a quiet pass — an absent root, a
+ # tree resolving to zero pages, or a page that cannot be read all exit 1
+ # naming what could not be read (#4690 / #7484).
+ #
+ # Invoked as `node` rather than through a `pnpm check:*` alias, same as
+ # the aggregator-roster step below: that alias belongs in root
+ # package.json, declared territory of the @changesets/cli v3 migration
+ # lane (#9465) while it runs. Dependency-free filesystem read, sub-second
+ # over the whole corpus.
+ - name: Docs frontmatter parses
+ run: |
+ node scripts/check-doc-frontmatter.mjs --self-test
+ node scripts/check-doc-frontmatter.mjs
+
  # #7484 docs anchors: `lychee.toml` sets `include_fragments = "none"`, so
  # the `Check Documentation Links` job resolves a link's FILE and never its
  # `#anchor` — measured with the pinned lychee 0.24.2 under the CI argv, a