docs: publish generated API reference

[mikaello]

Summary

• generate a searchable static API reference from ReScript's bundled rescript-tools doc output
• use the documented src/TinyColor.resi as the single source of truth for the public API
• infer documentation sections from each extracted item's kind, with no function-name allowlists or denylists
• run the generator as native TypeScript on Node 26 without a loader or transpiler
• publish the HTML site and raw api.json through GitHub Pages
• validate documentation builds on pull requests without deploying them

Dependency

This PR is stacked on #74, which defines and documents the public interface.
Merge #74 first, then retarget this PR to master.

Testing

• npm run build
• npx --yes node@26 scripts/generate-docs.mts
• npm run check
• npm test (220 tests)
• browser smoke test for layout and API filtering

Deployment note

GitHub Pages is not enabled for this repository yet.
After merging, select Settings → Pages → Build and deployment → GitHub Actions once; subsequent pushes to master deploy automatically.