A forum is a regular channel where every top-level message is a topic.
Replies go in the message's thread, the topic shows its reply count, and a
reply bumps the topic to the newest end of the channel, so old topics
resurface instead of sinking. Toggle it in Channel Functions or tick Forum
when creating a channel.
The history query orders topics by their latest activity, with cursors
resolved to activity stamps so paging keeps working, and topics never
compact into each other so a bump can move the node in place. Covered by an
integration test that boots a scratch server.
ancsemi