docs: close ProChat website quality milestone

[stevewesthoek]

Summary

• Reconcile roadmap, repo status, and implementation plan with deployed renderer revision 59a9c61.
• Record the 24fps/240-frame scroll-cache correction and successful production verification.
• Close the website milestone while handing off stale Mastermind source/index metadata separately, and name the LCP follow-up.

Validation

• Documentation links are valid.
• ✅ Environment documentation is synchronized.
• Documentation-only changes; repository workflow disables production deployment for docs-only merges.