StampRow
internal class StampRow(val contentKey: String, val shard: String, val length: Long, val mtime: Long, val source: String)
One mods.stamp line. Named rather than a tuple: same-typed fields in positional form are an argument order nobody can get wrong at a glance, and getting it wrong here reads back as a valid file.
length and mtime are the shard's own as stamped. Every rewrite is a new file, so a row the stamp never caught up with — a kill before publishStamps, or its write failing — stops vouching for bytes it never saw.