Use Gradle setup action in CI workflows

Replace manual gradlew permission and caching with the official
gradle/actions/setup-gradle action for better maintainability.

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

Co-Authored-By: Claude <[email protected]>

Author: nakamura-to

.github/workflows/ci.yml

@@ -19,8 +19,8 @@ jobs:
           distribution: 'zulu'
           java-version: 21
 
-      - name: Grant execute permission for ./gradlew
-        run: chmod +x gradlew
+      - name: Set up Gradle
+        uses: gradle/actions/[email protected]
 
       - name: Build plugin
         run: ./gradlew build

.github/workflows/release.yml

@@ -48,18 +48,8 @@ jobs:
         with:
           token: ${{ secrets.REPO_ACCESS_TOKEN }}
 
-      - name: Grant execute permission for gradlew
-        run: chmod +x gradlew
-
-      - name: Cache Gradle
-        uses: actions/cache@v4
-        with:
-          path: |
-            ~/.gradle/caches
-            ~/.gradle/wrapper
-          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*') }}
-          restore-keys: |
-            ${{ runner.os }}-gradle-
+      - name: Set up Gradle
+        uses: gradle/actions/[email protected]
 
       - name: Release ${{ env.RELEASE_VERSION }}
         run: |