Add GitHub Pages deployment workflow for website/

The smallest correct path to publish the static landing page:

- `.github/workflows/pages.yml` uses the official actions/configure-pages
  + upload-pages-artifact + deploy-pages chain to upload ./website as
  the Pages site on every push to main that touches website/ or the
  workflow itself, plus a workflow_dispatch trigger for the first
  manual deploy.
- No content changes to the landing page, no framework, no build step —
  pure HTML + CSS uploaded as-is.
- Not chosen: moving website/ into docs/ to use the legacy "Deploy from
  a branch" path. docs/ already holds developer-facing API.md /
  DEMO_SCRIPT.md / assets; mixing those with the marketing landing page
  would conflate concerns and start exposing internal docs at the Pages
  URL.

One-time manual setup on GitHub (cannot be done from a workflow file):
  Settings -> Pages -> Build and deployment -> Source: GitHub Actions

After that, every push to main that touches website/ auto-publishes.
The first deploy can be triggered from the Actions tab via
workflow_dispatch. The site URL appears as the environment URL on the
workflow run and will default to https://<owner>.github.io/<repo>/.

Verified: YAML parses cleanly; the upload path ./website exists with
index.html; official action versions pinned (checkout@v4,
configure-pages@v5, upload-pages-artifact@v3, deploy-pages@v4).

.github/workflows/pages.yml

@@ -0,0 +1,56 @@
+# Deploy the website/ landing page to GitHub Pages.
+#
+# One-time manual setup on GitHub (cannot be done from a workflow file):
+#   Settings -> Pages -> Build and deployment -> Source: GitHub Actions
+#
+# After that, every push to main that touches website/ (or this workflow
+# itself) auto-publishes. The first deploy can also be kicked off
+# manually from the Actions tab (the workflow_dispatch trigger below).
+# The published URL appears as the environment URL on the workflow run
+# and will be https://<owner>.github.io/<repo>/ by default.
+
+name: Deploy website to GitHub Pages
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'website/**'
+      - '.github/workflows/pages.yml'
+  workflow_dispatch:
+
+# Minimum permissions the official Pages actions need.
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# One concurrent deploy at a time. Finish in-progress runs rather than
+# canceling them so a deploy already underway isn't truncated.
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Configure Pages
+        uses: actions/configure-pages@v5
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          # Static landing page is self-contained under website/.
+          # No build step — pure HTML + CSS, no framework.
+          path: ./website
+
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4