Android CI on GitHub Actions

Gradle re-resolves dependencies and the emulator has no hardware acceleration.

Why it happens

~/.gradle is cold and GitHub-hosted Linux runners do not expose /dev/kvm on standard tiers.

What to change

1. Cache ~/.gradle/caches and ~/.android/avd
2. Run on a runner that exposes KVM so the emulator is hardware accelerated
3. Enable the Gradle configuration cache and build cache
4. Split unit tests and instrumentation tests into separate jobs

Android on runnerhut

jobs:
  test:
    runs-on: runnerhut-8vcpu-ubuntu-2404
    steps:
      - uses: actions/checkout@v4
      - uses: gradle/actions/setup-gradle@v4
      - run: ./gradlew testDebugUnitTest --build-cache
      - uses: reactivecircus/android-emulator-runner@v2
        with: { api-level: 34, script: ./gradlew connectedCheck }

The only runnerhut-specific line is `runs-on: runnerhut-8vcpu-ubuntu-2404`. Everything else is standard GitHub Actions — the same actions, the same secrets and the same permissions model you use today.