feat: separate plugin and skills

[christso]

currently skills, hooks and other artifacts need to be uniquely named otherwise links will be broken (because plugin-name or hash is appended to the artifact). This only works for specific marketplaces where they follow unique naming standards.

This is fine for internal plugins since we control the naming. But doesn't work for public plugins like superpowers which have names conflicting with other plugins.

perhaps we should have an option where prefix are always appended to artifact names to have proper namespacing.