String.prototype.replace treats $&/$1/$` in the replacement as patterns. A future
skill description containing $ (e.g. referencing $B/$D) would silently corrupt the
generated frontmatter. Use a function replacer. Behavior-preserving for all current
descriptions (regen produces no diff).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>