Agent Skills: update-spatie-docs

Update Spatie package documentation on spatie.be by re-importing docs for a given repo. Use after merging a PR that touches docs/, or when the user says 'update docs for [package]', 'rebuild docs for [repo]', 'import docs for [repo]', or invokes /update-spatie-docs [repo-name]. Takes a repo name argument (e.g., 'backup', 'laravel-medialibrary', 'laravel-pdf').