libtmux.control:cancel-request

Request cancellation; return true only when this call changes live work. Queued work is removed without dispatch or connection closure. Active work closes its connection and retires unissued queued requests. The worker records write progress before publishing :CANCELLED; await it to inspect that evidence. Cancellation winning before completion preserves :CANCELLED; an already terminal request is unchanged. No command is replayed and dispatched effects are not undone.