Keys unreachable by reference from ANY owned root — dead minted keys the encoder emitted but nothing uses (dedup/merge re-keyed their would-be referencers; the decoder's compress prunes them). Never emitted; totality is Owners + Dead = all keys, and owned nodes never reference dead keys (both invariants pinned by the integration suite). Encoder-side cleanup (don't emit unreferenced minted keys) is a backlog item, not load-bearing.