Enable Bazel caching in CI

All three cache layers were disabled by default in setup-bazel,
causing full rebuilds (~1100 actions) on every run. Enable
bazelisk, disk, and repository caches.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: birdayz

.github/workflows/test.yml

@@ -15,6 +15,10 @@ jobs:
 
     - name: Setup Bazel
       uses: useblacksmith/setup-bazel@v1
+      with:
+        bazelisk-cache: true
+        disk-cache: ${{ github.ref }}
+        repository-cache: true
 
     - name: Build and test
       run: bazelisk test //...