EphemeralEntry

An entry in an EphemeralMap: a nullable value tagged with a per-replica monotonic clock.

• value != null — the replica is present.

• value == null — the replica has departed gracefully (Yjs pattern: null-state + incremented clock). Any peer that merges a departure with a higher clock than a previously-seen presence entry will hide the replica.

The clock is used only for ordering within a single replica's slot — two replicas never compare clocks across slots, so cross-replica clock skew does not affect correctness.