Refactor GitHub Actions workflow to remove global pnpm installation and use pnpm/action-setup for version management

Author: wan92hen

.github/workflows/astro.yml

@@ -46,7 +46,6 @@ jobs:
             echo "lockfile=yarn.lock" >> $GITHUB_OUTPUT
             exit 0
           elif [ -f "${{ github.workspace }}/package.json" ]; then
-            npm -g install pnpm
             echo "manager=pnpm" >> $GITHUB_OUTPUT
             echo "command=install" >> $GITHUB_OUTPUT
             echo "runner=npx --no-install" >> $GITHUB_OUTPUT
@@ -62,6 +61,11 @@ jobs:
           node-version: "24"
           cache: ${{ steps.detect-package-manager.outputs.manager }}
           cache-dependency-path: ${{ env.BUILD_PATH }}/${{ steps.detect-package-manager.outputs.lockfile }}
+      - name: Setup pnpm
+        if: steps.detect-package-manager.outputs.manager == 'pnpm'
+        uses: pnpm/action-setup@v4
+        with:
+          version: 11        
       - name: Setup Pages
         id: pages
         uses: actions/configure-pages@v6