Refactor workflow

- Rename workflow to 'Build'
- Add push trigger on main branch
- Cancel workflow only when the run is NOT on `main` branch
- Update Gradle setup

Author: kpavlov

.github/workflows/validate-pr.yml renamed to .github/workflows/build.yml

@@ -1,13 +1,16 @@
-name: Validate PR
+name: Build
 
 on:
   workflow_dispatch:
   pull_request:
     branches: [ main ]
+  push:
+    branches: [ main ]
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
-  cancel-in-progress: true
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  # Cancel only when the run is NOT on `main` branch
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main'  }}
 
 jobs:
   validate-pr:
@@ -24,8 +27,11 @@ jobs:
 
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v4
+        with:
+          add-job-summary: 'always'
+          cache-read-only: true
 
-      - name: Clean Build with Gradle
+      - name: Build with Gradle
         run: ./gradlew clean build
 
       - name: Upload JUnit test results
@@ -36,7 +42,7 @@ jobs:
           path: '**/build/test-results/test/*.xml'
 
       - name: Disable Auto-Merge on Fail
-        if: failure()
+        if: failure() && github.event_name != 'pull_request'
         run: gh pr merge --disable-auto "$PR_URL"
         env:
           PR_URL: ${{github.event.pull_request.html_url}}