debugPreview function
Utility for callers: List<int> -> jsonEncode(...) doesn't hit
arg limits, but a helper avoids duplicating this everywhere in
bin/ demos.
Implementation
String debugPreview(List<int> ids, int max) {
if (ids.length <= max) return jsonEncode(ids);
return '${jsonEncode(ids.sublist(0, max))} ...(${ids.length} total)';
}