Align public docs and maintainer guidance with the current 1,304-skill catalog state and v8.4.0 release copy.
Refresh README credits for newly imported external sources, update user-facing count references, and document the post-release docs realignment in the changelog and walkthrough.
Consolidate the repository into clearer apps, tools, and layered docs areas so contributors can navigate and maintain it more reliably. Align validation, metadata sync, and CI around the same canonical workflow to reduce drift across local checks and GitHub Actions.
