Create Skill skill: what it does and how to install it

What it does. Guides creation of a new agent skill by validating its name, drafting routing-focused frontmatter, building the directory structure and writing actionable workflow sections. It also covers optional bundled files, CODEOWNERS updates, validator checks and adding an evaluation.

When to use it. Use for new skills, SKILL.md generation and repository setup. Do not use it to modify existing skills, fix failed evaluations, write eval.yaml independently or create custom agents.