listSaveSlots method
List all available save slots.
Returns cached information if available, otherwise reads from disk.
Backup (.backup.json) and temporary (.tmp) files are not slots.
Implementation
Future<List<SaveSlotInfo>> listSaveSlots() async {
if (_cachedSlots == null) {
await _refreshSlotCache();
}
return List.unmodifiable(_cachedSlots ?? []);
}