storedPackageDirectories property
Lists all locally cached package directories.
Returns a read-only list of paths.
Implementation
List<String> get storedPackageDirectories {
  if (!_storageDirectory.existsSync()) return const [];
  return UnmodifiableListView(
    _storageDirectory
        .listSync()
        .whereType<Directory>()
        .where((dir) => p.basename(dir.path).contains('@'))
        .map((dir) => dir.path)
        .toList(),
  );
}