Generated SKILL.md frontmatter emitted the catalog-trimmed description: as a
plain YAML scalar. A description with an interior ": " (e.g. "Ship workflow:
detect...") parses as a nested mapping under strict YAML loaders, so Codex/OpenAI
skill loading rejected those skills.
applyCatalogTrim now routes the value through toYamlInlineScalar, which quotes
(via JSON.stringify) only when a plain scalar would be invalid — interior ": ",
inline " #", leading indicator char, or surrounding whitespace. Strings that are
already valid plain scalars pass through unchanged to keep regen diffs small.
The frontmatter test now parses every generated block (Claude + Codex hosts) with
Bun.YAML.parse instead of string-checking that name:/description: substrings exist,
so the regression can't reappear. Runs under `bun test` (already in CI).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>