const LISTING: u64 = _; // 67_108_864u64Expand description
A listing is never read past this: some 130,000 names, read a response
at a time (read_listing), never held whole. Until 17 October 2026 a
listing was read whole up to 4 MiB, and blobs/ past some 8,700 sealed
files failed every step (review of 17 October 2026, M4).