Remove starter and work-in-progress copy

[hauptmedia]

Summary

• remove the public work-in-progress announcement override
• delete the default Docusaurus tutorial intro page
• replace starter README copy with project-specific setup instructions
• update homepage metadata, CTA links, and feature copy
• include the TypeScript 6 deprecation setting so the branch typechecks independently

Verification

• npm run typecheck
• npm run build (passes; reports existing broken link/anchor warnings already addressed by Fix docs link checks and enforce quality gates #115)
• Browser check at http://127.0.0.1:3010/ for desktop DOM and 390px mobile viewport

Depends on no code changes from #115, but #115 removes the pre-existing Docusaurus link/anchor warnings from main.