feat: split skills into standard + ClawHub variants

feat: declare all config paths, add file backups before writes

fix: use single-line valid JSON for metadata frontmatter

chore: add user-invocable: true to all skill frontmatter

chore: add node bin requirement and clarify API key save locations

feat: passwordless CLI auth flow, streamlined help text

update skills: flexible channel/playlist params, openclaw branding, openapi link

Update OpenClaw install command to npx clawhub@latest pattern

Initial commit: YouTube Skills for AI Agents