Deploy site via GitHub Actions instead of branch-based Pages

.github/workflows/deploy.yml

@@ -0,0 +1,69 @@
+name: Deploy Hugo site to Pages
+
+on:
+  push:
+    branches:
+      - trunk
+  pull_request:
+    branches:
+      - trunk
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow one concurrent deployment, skipping runs queued between the in-progress
+# run and the latest queued run, but never cancelling an in-progress deploy.
+concurrency:
+  group: pages-${{ github.ref }}
+  cancel-in-progress: false
+
+env:
+  HUGO_VERSION: 0.164.0
+
+jobs:
+  build:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Install Hugo CLI
+        run: |
+          wget -O "${{ runner.temp }}/hugo.deb" \
+            "https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_extended_${HUGO_VERSION}_linux-amd64.deb"
+          sudo dpkg -i "${{ runner.temp }}/hugo.deb"
+
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          submodules: recursive
+          fetch-depth: 0
+
+      - name: Setup Pages
+        id: pages
+        uses: actions/configure-pages@v6
+
+      - name: Build
+        env:
+          HUGO_ENVIRONMENT: production
+          TZ: Europe/London
+        run: hugo --gc --minify
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v5
+        with:
+          # Matches publishDir in hugo.toml
+          path: ./docs
+
+  # Pull requests build only — deploying happens once the change lands on trunk.
+  deploy:
+    if: github.event_name != 'pull_request'
+    needs: build
+    runs-on: ubuntu-24.04
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v5