ci: add gradle validation check to pr workflow

.github/workflows/pr.yml

@@ -1,16 +1,21 @@
 name: on-pr
+
 permissions:
   contents: read
 
 on:
-    workflow_dispatch:
-    pull_request:
+  workflow_dispatch:
+  pull_request:
 
 jobs:
   format_check:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
+
+      - name: Verify Gradle Wrapper
+        uses: gradle/actions/wrapper-validation@v3
+
       - name: Set up JDK 21
         uses: actions/setup-java@v5
         with:
@@ -22,4 +27,4 @@ jobs:
         run: chmod +x gradlew
 
       - name: Run ktfmt
-        run: ./gradlew ktfmtCheck
+        run: ./gradlew ktfmtCheck