onPeerActivated re-emits a presence_update for every relationship-related
online native to the activating peer (relationship = friend with peer-stub /
DM-mate with peer-stub / replicatedInstances opt-in for peer origin). Scope
bounded by relationship count, not native count — flap recovery cost stays
proportional to actual interaction surface.
onPeerDeactivated flips every replicated stub from that peer to offline and
broadcasts a local presence_update so connected friends/DM-mates/space-co-members
see them disappear immediately, instead of seeing stale online until next signal.
Re-snapshot on every activation (incl. health-check unreachable→active flap)
is load-bearing for correctness — markPeerStubsOffline ran on the prior
deactivation and presence is not in the mutation log.
Jannis Braun