ci: stop caching entire ~/.gradle/caches (was ~4GB)

Match ForestryMC/IC2: Gitea uses setup-gradle cache-provider external
with no whole-home actions/cache. Keep wrapper-only cache so restores
stay small on the Windows Docker runner.

.github/workflows/gradle.yml

@@ -36,25 +36,23 @@ jobs:
         cache-jdk: true
 
     # Nest mirrors github.com/gradle/actions as actions/gradle-actions (also as gradle/actions).
-    # v5 rejects cache-provider; v6 supports it. Default on v6 is "enhanced" (commercial) —
-    # on Gitea use external and cache Gradle home with actions/cache below (org IC2/Forestry pattern).
+    # Match ForestryMC/IC2: on Gitea use cache-provider external (no setup-gradle Actions cache).
+    # Do NOT actions/cache the whole ~/.gradle/caches — that hit ~4GB here and OOM'd the
+    # Windows Docker runner on restore; siblings never cache that tree.
     - name: Setup Gradle
       uses: actions/gradle-actions/setup-gradle@v6
       with:
         cache-cleanup: never
         cache-provider: ${{ github.server_url == 'https://github.com' && 'basic' || 'external' }}
 
-    # Cache wrapper + dependency/build caches (covers what setup-gradle skips under external).
-    - name: Cache Gradle home
+    # Wrapper only (small). Dependency jars re-download when cold — same as org mod CI on Gitea.
+    - name: Cache Gradle wrapper
       uses: actions/cache@v4
       with:
         path: |
-          ~/.gradle/caches
           ~/.gradle/wrapper
           .gradle/wrapper-neo
-        key: gradle-home-${{ runner.os }}-${{ hashFiles('gradle/wrapper/gradle-wrapper.properties', 'gradle/wrapper/GradleWrapperNeo.java', '**/libs.versions.toml', '**/*.gradle.kts', '**/*.gradle') }}
-        restore-keys: |
-          gradle-home-${{ runner.os }}-
+        key: gradle-wrapper-${{ runner.os }}-${{ hashFiles('gradle/wrapper/gradle-wrapper.properties', 'gradle/wrapper/GradleWrapperNeo.java') }}
 
     # Xvfb alone is not enough: JavaFX Glass needs GTK/X11 libs or Platform.startup fails with
     # GtkPlatformFactory "Internal Error" and :HMCL:test can hang (looks like a checkstyle stall).