Remove claude-design from the marketplace manifest and its catalog
README entry, and remove the playground-design-system entry from the
README. The catalog now lists 11 plugins.
Add scripts/check-public-links.mjs: fails when README.md or the
manifest links to an open/<name> repository missing from a tracked
PUBLIC_REPOS list. Chosen over the local retired-terms list because
that gate scans every tracked file, and historical docs plus
CONVENTIONS.md (which keep naming these repos on purpose) would hold
it red; a live visibility check could not be red before the repos
change visibility. Red on 5ba4a7a (6 hits), green after (0 of 36).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
