Scaffold a new skill in the singleton-skills plugin following all conventions. Use when creating a new skill from scratch — generates SKILL.md with correct frontmatter (name, description, argument-hint, license), a usage hint block, host-neutral argument guidance, scripts/ directory, and evals/evals.json stub. Trigger on: "scaffold a skill", "create a new skill", "new skill template", "skill boilerplate". Don't use when iterating on an existing skill — use dev-skill instead.
