Replace the bare onTurnAdopted callback and queuedFollowupLifecycle with one
turnAdoptionLifecycle surface (onSettled guaranteed via finally; adoption-loss
aborts queued steering turns without transcript replay), threaded through the
turn kernel and agent runner, exposed to plugins via
runtime.state.openChannelIngressDrain and the channel-outbound SDK barrel,
with surface budgets re-measured against the narrowed baselines (#108656).
16c14e5bbf
