Skill file layout

Each skill is its own folder under .agents/skills/ with a SKILL.md at the root. The full structure for this guide:

.agents/skills/
  ga-gsc-analyzer/
    SKILL.md
  landing-page-changelog/
    SKILL.md
    landing-page-changelog          # uv-script entry point
    scripts/cli.py
  humanizer/
    SKILL.md

ga-gsc-analyzer and humanizer are markdown-only - just write the SKILL.md files using the templates below. landing-page-changelog is the only one with code; we cover what it does below and you can write your own thin CLI to match (or skip it entirely - it's optional).