* fix: avoid GitHub API rate limits for the Node manifest
Large job matrices exhaust the shared GITHUB_TOKEN rate limit because each cold manifest lookup resolves a repository tree and blob through the REST API.
Use the fixed raw manifest and reuse it within a job. check-latest always refreshes it, and the authenticated API remains a fallback.
* fix: preserve check-latest manifest freshness
Raw manifest responses can remain cached for five minutes, so check-latest keeps the GitHub API path while normal setup steps reuse the job manifest.
* fix(manifest): use authenticated API with raw fallback
LTS resolution with check-latest cannot recover from API failures because it
bypasses raw retrieval. The disk cache cannot reduce requests across matrix
jobs and introduces unneeded state.
