fix(gen-skill-docs): quote frontmatter descriptions containing colons

[genisis0x]

Description

Closes #1778.

applyCatalogTrim in scripts/gen-skill-docs.ts rewrites the trimmed catalog description back into SKILL.md frontmatter as a plain YAML scalar:

description: Set up gbrain for this coding agent: install the CLI, ... (gstack)

When the description contains ": " (or a trailing colon), a strict YAML parser reads the second colon as a mapping separator and rejects the document:

invalid YAML: mapping values are not allowed in this context

Codex/OpenAI skill loading uses a strict parser, so every affected skill was silently skipped.

Change

• Add toYamlPlainOrQuoted(value): returns the value unchanged when it is a valid plain scalar, otherwise emits a double-quoted scalar (escaping \ and "). Quoting triggers only on : / trailing colon / leading YAML indicator chars, so existing colon-free descriptions are byte-for-byte unchanged.
• Use it at the trim rewrite site.
• Regenerated SKILL.md for the 8 skills whose descriptions contain colons (design-consultation, design-html, design-review, design-shotgun, guard, plan-tune, setup-gbrain, ship).

Testing

• bun test test/gen-skill-docs.test.ts — 389 pass (incl. per-host --dry-run freshness across all hosts).
• bun test test/skill-validation.test.ts — 329 pass.
• Regenerated docs are fresh (gen:skill-docs for claude/codex/factory and the remaining hosts produces no further diff).

[jbetala7]

Collision check: #1739 and #1752 already cover this same generated-SKILL frontmatter bug.

#1739 changes scripts/gen-skill-docs.ts to quote the generated description and regenerates the catalog. #1752 is the active v1.52.3.0 frontmatter branch with the generator-level quote, the full regenerated SKILL.md set, a new skill-frontmatter-check script/workflow, and validation coverage. This PR fixes the same symptom for #1778, but it only regenerates the eight currently failing root skills and does not add the validation gate, so it is a narrower duplicate.

Suggested path: port the Closes #1778 linkage or any repro evidence into whichever of #1752/#1739 maintainers choose as canonical, rather than landing a third branch for the same fix.

[genisis0x]

Closing as superseded: main now handles colon-containing frontmatter descriptions via toYamlInlineScalar in scripts/gen-skill-docs.ts, so this quoting change is no longer needed.