Separate weekly tasks for tarball-integrity checks. (#8858)

Author: isoos

CHANGELOG.md

@@ -6,6 +6,7 @@ AppEngine version, listed here to ease deployment and troubleshooting.
  * Upgraded stable Dart analysis SDK to `3.8.3`
  * Upgraded stable Flutter analysis SDK to `3.32.8`.
  * Upgraded pana to `0.22.22`.
+ * Note: Tarball-related integrity checks are run in a separate weekly task (`check-tarball-integrity`).
 
 ## `20250804t140400-all`
  * Bump runtimeVersion to `2025.07.14`.

app/lib/package/tarball_storage.dart

@@ -61,6 +61,19 @@ class TarballStorage {
   String getCanonicalBucketAbsoluteObjectName(String package, String version) =>
       _canonicalBucket.absoluteObjectName(tarballObjectName(package, version));
 
+  /// Get a list of package names in the canonical bucket.
+  Future<List<String>> listPackagesInCanonicalBucket() async {
+    final items = await _canonicalBucket.listAllItemsWithRetry(
+        prefix: 'packages/', delimiter: '-');
+    final packages = items
+        .where((i) => i.isDirectory)
+        .map((i) => i.name)
+        .map((name) => name.substring(9).split('-').first)
+        .toSet()
+        .toList();
+    return packages;
+  }
+
   /// Get map from `version` to [SourceObjectInfo] for each version of [package] in
   /// canonical bucket.
   Future<Map<String, SourceObjectInfo>> listVersionsInCanonicalBucket(