Add project marketing website

.github/workflows/pages.yml

@@ -0,0 +1,42 @@
+# Publishes the static marketing site in website/ to GitHub Pages.
+# Enable it once under Settings -> Pages -> Source: "GitHub Actions".
+name: pages
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "website/**"
+      - "docs/**"
+      - "tools/build-docs.py"
+      - ".github/workflows/pages.yml"
+  workflow_dispatch:
+
+# Allow this workflow to publish a Pages deployment.
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# One concurrent deploy; let an in-progress run finish.
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/configure-pages@v5
+      # Regenerate the styled doc pages from docs/*.md so the deploy is never
+      # stale (no extra dependencies — the generator is pure-Python stdlib).
+      - run: python3 tools/build-docs.py
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: website
+      - id: deployment
+        uses: actions/deploy-pages@v4