Resolve GitHub Actions pnpm conflict and enable PR workflow validation

.github/module-cache/action.yaml

@@ -7,21 +7,14 @@ inputs:
 runs:
   using: 'composite'
   steps:
-    - name: Get pnpm version from package.json
-      id: get-pnpm-version
-      run: |
-        node -e "const p=require('./package.json').packageManager||''; const v=(p.split('@')[1]||'10'); console.log('pnpm-version='+v)" >> $GITHUB_OUTPUT
-      shell: bash
-
     - name: Install pnpm
       uses: pnpm/action-setup@v4
-      with:
-        version: ${{ steps.get-pnpm-version.outputs.pnpm-version }}
+
     - name: Setup node
       uses: actions/setup-node@v5
       with:
         node-version: ${{ inputs.node-version }}
-        cache: 'pnpm'
+
     - name: Install dependencies
       run: |
         pnpm config set auto-install-peers false

.github/workflows/action.yml

@@ -1,6 +1,9 @@
 name: Deploy to GitHub Pages
 
 on:
+  pull_request:
+    branches:
+      - main
   push:
     branches:
       - main
@@ -14,18 +17,14 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v6
-      - name: Setup pnpm
-        uses: pnpm/action-setup@v6
-        with:
-          version: 11
-          cache: true
       - name: Setup Node, install dependencies, and cache node modules, build dist artifacts
         uses: ./.github/build-artifacts
         with:
           node-version: ${{ matrix.node }}
 
   deploy:
     needs: build
+    if: github.event_name == 'push'
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -34,11 +33,6 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v6
-      - name: Setup pnpm
-        uses: pnpm/action-setup@v6
-        with:
-          version: 11
-          cache: true
       # Set up GitHub Actions caching for Wireit.
       # - uses: google/wireit@setup-github-actions-caching/v2