fn seat_liveness(update: &SessionUpdate) -> boolExpand description
The seat events a board row’s stale mark is read from.
seat_is_live reads the domain/agent registry and the worker registry,
and these are the frames that change either: a seat starting, connecting,
being replaced, releasing, failing to connect, or a worker’s status
moving. Turn frames are not here - a task write is what moves a row’s work,
and a page’s own beat advances its clocks.
The coverage is not exact. A session task exiting and a worktree
rollback release the handle with no frame of their own, and Spawning
fires before the handle exists - so in those windows a row’s mark can lag
until the seat’s next covered frame, or until the page’s beat re-reads.