alice in one and bob in the other.
- In alice: create a 🔒 encrypted room, copy the room_id,
- then pick bob as target and Invite to this room.
- In bob: paste that room_id and Join.
- Type in both → messages appear live on each side.
- In alice: Kick bob → bob stops seeing new messages (forward secrecy: the room
- key rotates and bob no longer holds it).
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