Add GitHub Actions workflows for PR preview builds and cleanup

.github/workflows/pr-preview-cleanup.yml

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+name: PR Preview Cleanup
+
+on:
+  pull_request_target:
+    types: [closed]
+
+permissions:
+  contents: write
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          ref: gh-pages
+          fetch-depth: 0
+
+      - name: Remove PR preview directory
+        run: |
+          PR_NUM=${{ github.event.pull_request.number }}
+          PREVIEW_DIR="pr-${PR_NUM}"
+
+          if [ -d "$PREVIEW_DIR" ]; then
+            echo "Removing preview directory: $PREVIEW_DIR"
+            rm -rf "$PREVIEW_DIR"
+
+            # Check if there are any changes to commit
+            if [ -n "$(git status --porcelain)" ]; then
+              git config user.name "github-actions[bot]"
+              git config user.email "github-actions[bot]@users.noreply.github.com"
+              git add -A
+              git commit -m "Remove preview for PR #${PR_NUM}"
+              git push
+              echo "Removed preview directory: $PREVIEW_DIR"
+            else
+              echo "No changes to commit"
+            fi
+          else
+            echo "Preview directory $PREVIEW_DIR does not exist, skipping cleanup"
+          fi
+

.github/workflows/pr-preview.yml

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+name: PR Preview Build and Deploy
+
+on:
+  pull_request_target:
+    types: [opened, synchronize, reopened]
+
+permissions:
+  contents: write
+  pull-requests: write
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pr-preview-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout base repository
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.base.ref }}
+          fetch-depth: 0
+
+      - name: Checkout PR branch
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          path: pr-source
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.1'
+          bundler-cache: true
+
+      - name: Install Asciidoctor
+        run: gem install asciidoctor
+
+      - name: Build HTML from AsciiDoc
+        working-directory: pr-source/supplementary_style_guide
+        run: asciidoctor main.adoc
+
+      - name: Prepare preview directory
+        run: |
+          PR_NUM=${{ github.event.pull_request.number }}
+          PREVIEW_DIR="deploy/pr-${PR_NUM}"
+          mkdir -p "${PREVIEW_DIR}"
+
+          # Copy the generated HTML file from PR source
+          cp pr-source/supplementary_style_guide/main.html "${PREVIEW_DIR}/"
+
+          # Copy images directory preserving structure
+          if [ -d "pr-source/supplementary_style_guide/images" ]; then
+            cp -r pr-source/supplementary_style_guide/images "${PREVIEW_DIR}/"
+          fi
+
+          # Copy any other image files preserving directory structure
+          find pr-source/supplementary_style_guide -type f \( -name "*.png" -o -name "*.jpg" -o -name "*.jpeg" -o -name "*.gif" -o -name "*.svg" \) | while read -r file; do
+            rel_path="${file#pr-source/supplementary_style_guide/}"
+            target_dir="${PREVIEW_DIR}/$(dirname "$rel_path")"
+            mkdir -p "$target_dir"
+            cp "$file" "$target_dir/"
+          done
+
+      - name: Deploy to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./deploy/pr-${{ github.event.pull_request.number }}
+          destination_dir: pr-${{ github.event.pull_request.number }}
+          keep_files: true
+
+      - name: Generate preview URL
+        id: preview-url
+        run: |
+          REPO_NAME="${{ github.repository }}"
+          PREVIEW_URL="https://${{ github.repository_owner }}.github.io/${REPO_NAME#*/}/pr-${{ github.event.pull_request.number }}/main.html"
+          echo "url=${PREVIEW_URL}" >> $GITHUB_OUTPUT
+          echo "Preview URL: ${PREVIEW_URL}"
+
+      - name: Find existing comment
+        uses: peter-evans/find-comment@v3
+        id: find-comment
+        with:
+          issue-number: ${{ github.event.pull_request.number }}
+          comment-author: 'github-actions[bot]'
+          body-includes: 'Preview Build'
+
+      - name: Create or update PR comment
+        uses: peter-evans/create-or-update-comment@v4
+        with:
+          comment-id: ${{ steps.find-comment.outputs.comment-id }}
+          issue-number: ${{ github.event.pull_request.number }}
+          body: |
+            ## Preview Build
+
+            A preview of this PR has been built and deployed.
+
+            **Preview URL:** [${{ steps.preview-url.outputs.url }}](${{ steps.preview-url.outputs.url }})
+
+            This preview will be updated automatically when new commits are pushed to this PR.
+
+            ---
+            *This comment is automatically generated by the PR Preview workflow.*
+