Voice and video calls, and you can see when a message was read

Messaging grew calling. A call is keyed by scope rather than by a chat table, which is what lets the iOS app ring from a DM and this app answer it from a workspace thread — either side can start or pick up the other's call. On iOS it rings through the phone's own call screen via CallKit, so it behaves like a real call rather than a notification you might miss.