deinit

    fn deinit(cancel_region: *CancelRegion) void {
        if (cancel_region.status.requested) {
            @branchHint(.likely);
            _ = cancel_region.fiber.cancel_status.changeAwaiting(
                cancel_region.status.awaiting,
                .nothing,
            );
        }
        cancel_region.* = undefined;
    }