ci(e2e): route matrix emulator + system-image install through the #389-hardened installer

The E2E (33) matrix leg deadlocked the merge queue for ~2h when
android-emulator-runner's un-guarded "Create AVD and generate snapshot" step
died with "Error on ZipFile unknown archive" installing a corrupt Android
Emulator SDK zip. #389 hardened the platform/build-tools install (SHA-verify ->
reject-corrupt -> purge -> re-download) but left the emulator + system-image
install to the action, un-guarded.

Pre-install "emulator" + "system-images;android-<api>;google_apis;x86_64"
through setup_android_sdk.py before the emulator-runner steps, so a corrupt zip
is self-healed here and the action then finds both packages already installed
and skips its fragile fetch. Runs on both AVD-cache hit and miss (the emulator
binary + image live under the SDK root, not the ~/.android AVD-snapshot cache,
so they must be present for even a cached AVD to boot). Not added to the
android-sdk-v1 cache (kept small); re-install is a fast sdkmanager no-op when
already present.

The e2e-preview (API 37) job already routes emulator + system image through the
hardened installer, so no change there. setup_android_sdk.py already handles
these package ids generically; add a unit assertion pinning the matrix's
google_apis/x86_64 id to the correct purge path.

Closes #443

.github/scripts/test_setup_android_sdk.py

@@ -36,6 +36,13 @@ class PackageDirTests(unittest.TestCase):
             sdk.package_dir(root, "system-images;android-37.0;google_apis_ps16k;x86_64"),
             os.path.join(root, "system-images", "android-37.0", "google_apis_ps16k", "x86_64"),
         )
+        # The matrix e2e legs (#443) pre-install the google_apis/x86_64 image for their API level
+        # through this same installer, so a corrupt emulator/system-image zip is purged from the
+        # right dir on retry — assert that (non-ps16k) id maps correctly too.
+        self.assertEqual(
+            sdk.package_dir(root, "system-images;android-33;google_apis;x86_64"),
+            os.path.join(root, "system-images", "android-33", "google_apis", "x86_64"),
+        )
 
     def test_flat_ids_map_to_single_dir(self):
         root = os.path.join("opt", "sdk")