Add token generator and generated artifacts

[Drixled]

Summary

• Add the standalone node build token generator under build/ with culori validation/conversion.
• Commit generated token outputs: src/tokens.web.css, src/tokens.ts, and src/tokens.host-map.md.
• Add CI staleness checking so generated files cannot drift from tokens.json.
• Update the playground save menu: Save Tokens, undo-last-save, and dropdown actions for Generate Tokens and Download.
• Remove Agentation from the playground and move to a root pnpm workspace/lockfile.
• Update README and the execution checklist for T1.2.

Validation

• pnpm install --frozen-lockfile
• node build
• pnpm --dir playground build
• pnpm --dir playground exec tsc --noEmit
• git diff --check