feat: run bun pages:dev in background during build

- Install bun runtime for faster package management
- Start pages:dev server in background during build process
- Track dev server PID for proper cleanup
- Ensure dev server is stopped after build completion

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.github/workflows/release-pages.yml

@@ -96,12 +96,31 @@ jobs:
           workflow_conclusion: success
           path: ./.pages/vitest-reports
 
+      - name: Install bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Start pages dev server in background
+        run: |
+          bun pages:dev &
+          echo "Started bun pages:dev in background (PID: $!)"
+          echo "DEV_SERVER_PID=$!" >> $GITHUB_ENV
+
       - name: Build static assets (with artifact reuse)
         run: ./scripts/build-pages.sh
 
       - name: Setup Pages
         uses: actions/configure-pages@v4
 
+      - name: Stop pages dev server
+        if: always()
+        run: |
+          if [ -n "$DEV_SERVER_PID" ]; then
+            kill $DEV_SERVER_PID 2>/dev/null || true
+            echo "Stopped pages dev server (PID: $DEV_SERVER_PID)"
+          fi
+
       - name: Upload built pages as cache
         uses: actions/upload-pages-artifact@v4
         with: