ci: add GitHub Pages deployment workflow

Automate site deployment on pushes to main. Workflow compiles TypeScript,
runs tests as a gate, and assembles the published site from index.html,
dist/, and trips.js.example (copied as trips.js). This ensures the
published page serves only example data; real travel data never leaves
the local machine.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: indradhanush

.github/workflows/pages.yml

@@ -0,0 +1,52 @@
+name: Deploy to GitHub Pages
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Build
+        run: npx --yes -p typescript@5 tsc -p .
+
+      - name: Test
+        run: node --test test/
+
+      # The published page serves the example data; real trips.js never
+      # leaves the local machine.
+      - name: Assemble site
+        run: |
+          mkdir _site
+          cp index.html _site/
+          cp -R dist _site/dist
+          cp trips.js.example _site/trips.js
+
+      - uses: actions/configure-pages@v5
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: _site
+
+      - id: deployment
+        uses: actions/deploy-pages@v4