Add GitHub Pages deploy workflow

- Trigger on push to main and manual dispatch
- Use Node 20, install deps, compute base path
- Build and upload dist, then deploy with concurrency control

Author: aurexav

.github/workflows/deploy-pages.yml

@@ -0,0 +1,61 @@
+name: Deploy the site to GitHub Pages.
+
+on:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: github-pages
+  cancel-in-progress: true
+
+jobs:
+  deploy:
+    name: Deploy.
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Check out the repository.
+        uses: actions/checkout@v4
+
+      - name: Set up Node.js.
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
+      - name: Configure GitHub Pages.
+        uses: actions/configure-pages@v5
+
+      - name: Install dependencies.
+        run: npm install --no-audit --no-fund
+
+      - name: Determine the base path.
+        id: base
+        run: |
+          if [ "${{ github.event.repository.name }}" = "${{ github.repository_owner }}.github.io" ]; then
+            echo "base=/" >> "$GITHUB_OUTPUT"
+          else
+            echo "base=/${{ github.event.repository.name }}/" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Build the site.
+        env:
+          GEMINI_API_KEY: ${{ secrets.GEMINI_API_KEY || '' }}
+        run: npm run build -- --base="${{ steps.base.outputs.base }}"
+
+      - name: Upload the Pages artifact.
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: dist
+
+      - name: Deploy to GitHub Pages.
+        id: deployment
+        uses: actions/deploy-pages@v4