fix: cache AVD and retry emulator boot to stop balances-test CI flake

main's scheduled run has been failing most cycles since 2026-07-06 with
either a corrupted SDK package download (Error on ZipFile unknown archive)
or a plain emulator boot timeout - both manifest as adb never reaching
emulator-5554. The job never cached the AVD, so every single run re-hit
Google's SDK servers for a fresh system image download, keeping it exposed
to this exact flake on every run and every 8-hour schedule tick.

Cache the AVD (skips the download entirely once warm) and duplicate the
test-run step as a same-job retry for the residual flake (cold cache, or
a rare boot timeout even with a warm cache).

.github/workflows/balances_test.yml

@@ -44,13 +44,50 @@ jobs:
           sudo udevadm control --reload-rules
           sudo udevadm trigger --name-match=kvm
 
+      - name: AVD cache
+        uses: actions/cache@v4
+        id: avd-cache
+        with:
+          path: |
+            ~/.android/avd/*
+            ~/.android/adb*
+          key: avd-29-nexus6-x86_64-v1
+
+      - name: Create AVD and generate snapshot for caching
+        if: steps.avd-cache.outputs.cache-hit != 'true'
+        uses: reactivecircus/android-emulator-runner@v2
+        with:
+          disable-animations: false
+          profile: Nexus 6
+          api-level: 29
+          arch: x86_64
+          force-avd-creation: false
+          emulator-options: -no-window -gpu swiftshader_indirect -noaudio -no-boot-anim -camera-back none
+          script: echo "Generated AVD snapshot for caching."
+
       - name: Run tests
+        id: run-tests-attempt-1
+        continue-on-error: true
         uses: reactivecircus/android-emulator-runner@v2
         with:
           disable-animations: true
           profile: Nexus 6
           api-level: 29
           arch: x86_64
+          force-avd-creation: false
+          emulator-options: -no-window -gpu swiftshader_indirect -no-snapshot-save -noaudio -no-boot-anim
+          script: .github/scripts/run_balances_test.sh
+
+      - name: Run tests (retry - reactivecircus/android-emulator-runner flakes on SDK download/emulator boot)
+        if: steps.run-tests-attempt-1.outcome == 'failure'
+        uses: reactivecircus/android-emulator-runner@v2
+        with:
+          disable-animations: true
+          profile: Nexus 6
+          api-level: 29
+          arch: x86_64
+          force-avd-creation: false
+          emulator-options: -no-window -gpu swiftshader_indirect -no-snapshot-save -noaudio -no-boot-anim
           script: .github/scripts/run_balances_test.sh
 
       - uses: actions/upload-artifact@v4