feat(docs): Docusaurus site scaffold + Pages CI (PR #1/3)

[EtienneLescot]

What this PR does

Scaffolds the OpenScreen docs site (Docusaurus 3, monorepo under \website/) and adds a GitHub Pages deployment workflow. First of three PRs planned in the ROADMAP tier Stability & quality → Site & documentation (see PR #32).

• \website/: Docusaurus 3 site with TypeScript config, Infima-tweaked theme, minimal hero landing (gradient title, dual CTA, WIP badge, three-feature row) and a single \intro\ doc.
• .github/workflows/docs.yml: builds on PR (uploads artifact), deploys to GitHub Pages on push to \main. Concurrency group + minimal permissions.
• \website/postcss.config.cjs: overrides the monorepo Tailwind config so Docusaurus doesn't try to load it.

What's intentionally NOT in this PR

• Full docs migration from \docs/\ to \website/docs/\ — that lands in PR Bugs #3.
• Polished landing (real screenshots, bento grid, animations, Geist font, search local) — PR fix(cursor): native cursor overlay fixes for multi-display, crop, zoom and export consistency #2.
• ROADMAP tier entry lives in PR docs(roadmap): add 'Site & documentation' tier #32.

How to validate locally

\\sh
cd website
npm install
npm run typecheck
npm run build
npm run serve # http://localhost:3000/openscreen/
\\

Deploy setup (one-time, in repo Settings)

Before the deploy job actually ships:

1. Settings → Pages → Source = GitHub Actions
2. (optional) Custom domain follow-up — not in this PR

Until that's set, the deploy job will fail on \main\ push but the build job will pass and the PR preview artifact will be downloadable.

[EtienneLescot]

PR #1/3 ready for review. CI build green (artifact github-pages uploaded).

One manual step before merge — Settings → Pages → Source = \GitHub Actions. The deploy job is gated on push to \main, so without that toggle the first post-merge run will fail with a clear error. Fix is one click.

What's in this PR:

• \website/\ minimal Docusaurus 3 site (TypeScript, Infima-tweaked theme, gradient hero, intro doc)
• .github/workflows/docs.yml\ — build on PR, deploy on push to \main\

Follow-ups:

• PR fix(cursor): native cursor overlay fixes for multi-display, crop, zoom and export consistency #2 → polished landing (Geist, bento, animations, real demo)
• PR Bugs #3 → migrate \docs/\ → \website/docs/, full sidebar

[EtienneLescot]

@FabLrc

[EtienneLescot]

Closing as superseded — every commit in this branch is already on \main:

• \8176f47 feat(docs): scaffold Docusaurus 3 site + GitHub Pages CI\ (identical tree to \cce4524)
• \�6d8af3 style(website): biome auto-format for cce4524 website scaffold\ (fixes the 8 lint errors this PR was hitting)
• \8f1134e ci(docs): pin actions to commit SHAs in docs.yml\

Rebased onto \origin/main\ (\ix/pr-31-rebase) → 0 diff. Nothing left to merge.

PRs #2 and #3 in the docs-site tier can continue from the merged state on \main.