[RaphaelFakhri]

Summary: npm run check:skills now fails when a frontmatter value is an unquoted scalar that starts with a YAML indicator character.

Why: The frontmatter check exists so CI catches SKILL.md files that the skills CLI cannot parse (see #38). It currently accepts plain values such as description: `/plan` before coding or description: [Experimental] Run the factory. The skills CLI parses frontmatter with yaml, which rejects these values, so the CLI drops the skill from discovery without an error. Values that start with &, !, or # parse, but YAML treats the first token as an anchor, tag, or comment, so the description changes or disappears.

What changed:

• parsePlainScalar rejects plain values that start with [ ] { } , # & * ! | > ' " % @ or a backtick, or with -, ?, or : followed by whitespace. The error tells you to quote the value or use a folded block scalar, matching the existing : error.
• parseFrontmatter is exported, and main() runs only when the script is executed directly, so the parser can be unit tested.
• Added scripts/check-skill-frontmatter.test.mjs (built-in node:test, no new dependencies) and an npm test script.

How to test:

1. Run npm test. Both tests pass.
2. Run npm run check:skills. All existing skills remain valid.
3. Create skills/demo/SKILL.md with name: demo and description: `/plan` before coding, then run npm run check:skills. The check fails with plain scalars cannot start with ''. Before this change, it reported the file as valid, and npx skills@1.7.4 add ./ --list` did not list the skill.

Notes: No migrations or breaking changes. CI does not run npm test yet. Adding a step to .github/workflows/ci.yml is a possible follow-up.

Fixes #105

[steve8708]

thanks @RaphaelFakhri ! looks like we just need CI to pass

[RaphaelFakhri]

Rebased onto main. The check job failed because the branch predated the latest Agent Native skill exports. On the rebased branch, npm run check:skills, npm run check:agent-native-skills against current agent-native main, and npm test pass. The frontmatter check also accepts the skills added since, including efficient-orchestrator.