Function send_dispatch_turn_error 

pub(crate) fn send_dispatch_turn_error(
    workspace: &Workspace,
    key: SessionSlot,
    err: &DispatchError,
)

A failed prompt dispatch to a running target unwinds the echo’s already-opened turn: without this its bar counts forever and the bucket spinner never drops (mirrors the typed-submit compensation). Per-site warns stay at the call sites.