MEMBERSHIP_DRAIN

A conformance harness that cannot inject a membership drain — a peer leaving Seam.peers while the survivor's state stays us.tractat.kuilt.core.SeamState.Woven (no transport tear), the distinct event #1466 relied on (see SeamConformanceSuite.membershipDrainGap). Not a fabric gap — a harness gap: a strictly-2-peer mesh must latch us.tractat.kuilt.core.SeamState.Torn when its only link drops, so it cannot model a drain-without-tear at all; only an N-peer harness (e.g. the shared-roster InMemoryLoom) can drop one peer and leave the survivor Woven.