2026-03: GitHub Pages docs launch and publication policy

What changed

Added a VitePress-based docs site inside the repository
Added explicit legal and content-policy documents
Added a docs navigation layer over architecture, algorithm, AI, and API references
Added templates for future feature pages and update posts

The repository now has a stable public documentation surface distinct from the live product and internal operating detail.

New contributors and users can understand the project from a curated docs site instead of scanning the entire repository.

Future user-facing features should update at least one docs page or update post.