dx: structural CI — frontmatter, manifest, relative links, variant parity, version agreement

[CnxLuc]

This repo is prompt-ware — the markdown files are the program — and community PRs are already landing, with nothing checking that SKILL.md frontmatter stays valid, that .claude-plugin/plugin.json stays parseable, or that the relative links wiring SKILL.md to its references/*.md still resolve. A reference rename would silently break the skill for every installer. The audit playbook's own rule: "is there a one-command way to know the codebase works? If not, that's finding #1."

This adds the deterministic subset of that baseline (deliberately not LLM-behavioral evals):

• scripts/check.py — Python 3 stdlib only, no dependencies. Five checks:
  1. SKILL.md frontmatter present with non-empty name/description, name = improve
  2. plugin.json parses; name/version present; name matches the frontmatter
  3. every relative markdown link in the repo resolves (fenced code blocks skipped — plan-template.md is full of example links that must not be validated; plans/ output dirs skipped)
  4. all 9 invocation variants appear in both README.md and SKILL.md
  5. metadata.version in SKILL.md agrees with plugin.json version
• .github/workflows/check.yml — checkout + run the script on push/PR, nothing else.

Negative-tested: renaming references/audit-playbook.md fails the run naming the broken link in SKILL.md; restoring passes. The checker is green against current main as-is, so this PR is safe to merge independently of any other open PR.

🤖 Generated with Claude Code