sanitizeKey static method
Maps an arbitrary key (e.g. <user>@<node>) to a safe, stable identifier
component — usable as a filename (CLI) or a storage-key suffix (web).
Implementation
static String sanitizeKey(String key) {
final safe = key.replaceAll(RegExp(r'[^A-Za-z0-9_.@-]'), '_');
return safe.isEmpty ? '_' : safe;
}