add: deploy and test workflows for GitHub Pages

Astro build via GitHub Actions, deploy to GitHub Pages.
Test-on-push validates the build on every commit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: a6b8

.github/workflows/deploy.yml

@@ -0,0 +1,49 @@
+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: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npx astro build
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ./dist
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

.github/workflows/test-on-push.yml

@@ -0,0 +1,24 @@
+name: Run Tests on Push
+
+on: push
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Use Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build (Astro + Starlight)
+        run: npm run build