Delivered

A delivered-version-vector gossip from sender — sender's whole-room contiguous delivered VersionVector (`author → highest gap-free seq it has applied), the per-replica row of the matrix clock that decides causal stability for RGA GC (ADR-003 addendum v3, #262).

Kept separate from Ack deliberately: Ack is per-author progress on this replica's own deltas and rides the delta/ack cadence; Delivered is a cross-author whole-room snapshot gossiped on its own cadence (on local apply and on the anti-entropy tick). The recipient stores it as that peer's matrix row.