notifyActivity method
Notifies that activity has occurred on this transport connection, potentially due to activity on a multiplexed stream over it. This can be used by multiplexers to inform the connection manager.
Implementation
@override
void notifyActivity() {
// TODO: Implement if activity on a circuit connection should
// keep the underlying physical connection to the relay alive.
// This might involve calling recordActivity on the _manager for the
// actual physical connection to the relay, if this CircuitConnection
// is directly managed or can influence that.
// For now, providing an empty implementation.
// It already calls _manager.recordActivity(this) on read/write.
}