ci: add build workflow, dependabot config, and Pages deploy

- build.yml: hugo extended 0.154.0, runs on PR + main push, uploads
  exampleSite artifact for inspection
- deploy.yml: deploys exampleSite to GitHub Pages on main push using
  actions/configure-pages + actions/deploy-pages (modern flow, no
  gh-pages branch)
- dependabot.yml: weekly action version updates

One-time manual: enable Pages in repo settings (Source = GitHub Actions)
before deploy.yml will succeed.

themes/bonsai/.github/dependabot.yml

@@ -0,0 +1,11 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+      day: monday
+    open-pull-requests-limit: 5
+    commit-message:
+      prefix: chore
+      include: scope

themes/bonsai/.github/workflows/build.yml

@@ -0,0 +1,40 @@
+name: build
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+concurrency:
+  group: build-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+          fetch-depth: 0
+
+      - name: Setup Hugo Extended
+        uses: peaceiris/actions-hugo@v3
+        with:
+          hugo-version: '0.154.0'
+          extended: true
+
+      - name: Build exampleSite
+        working-directory: exampleSite
+        run: hugo --gc --minify --themesDir ../.. --printPathWarnings
+
+      - name: Upload built site
+        uses: actions/upload-artifact@v4
+        with:
+          name: exampleSite-public
+          path: exampleSite/public
+          retention-days: 7

themes/bonsai/.github/workflows/deploy.yml

@@ -0,0 +1,57 @@
+name: deploy
+
+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:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+          fetch-depth: 0
+
+      - id: pages
+        uses: actions/configure-pages@v5
+
+      - name: Setup Hugo Extended
+        uses: peaceiris/actions-hugo@v3
+        with:
+          hugo-version: '0.154.0'
+          extended: true
+
+      - name: Build with production baseURL
+        working-directory: exampleSite
+        run: |
+          hugo \
+            --gc \
+            --minify \
+            --themesDir ../.. \
+            --baseURL "${{ steps.pages.outputs.base_url }}/"
+
+      - name: Upload Pages artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: exampleSite/public
+
+  deploy:
+    needs: build
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    steps:
+      - id: deployment
+        uses: actions/deploy-pages@v4