The regex that extracts descriptions from YAML frontmatter did not
properly parse quoted values. Descriptions containing apostrophes
(e.g. "can't") produced invalid YAML when re-wrapped in single quotes.
Replace the naive regex with proper handling of single-quoted,
double-quoted, and unquoted YAML values, and escape inner single
quotes using YAML '' syntax before re-wrapping.
Add tests for transformToSkillFormat covering plain, double-quoted,
and single-quoted descriptions with embedded apostrophes.
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