Add custom Pages deploy workflow with cancel-in-progress: false

Replaces the built-in 'pages build and deployment' workflow so that
an in-progress deploy is never cancelled by a subsequent push.
New pushes queue behind the running deploy (collapsing to one pending
run), and the latest commit is deployed once the current one finishes.

Requires Pages source to be set to 'GitHub Actions' in repo settings.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sjh26

.github/workflows/deploy.yml

@@ -0,0 +1,45 @@
+name: Deploy Jekyll site to Pages
+
+on:
+  push:
+    branches: ["master"]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+
+      - name: Build with Jekyll
+        uses: actions/jekyll-build-pages@v1
+        with:
+          source: ./
+          destination: ./_site
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4