notify method
Triggers a change notification without modifying the value.
Notifies all subscribers that they should re-evaluate, even if the underlying value hasn't changed (e.g., in-place mutations).
Example:
final list = ListSignal([1, 2, 3]);
list.value.add(4);
list.notify(); // Force subscribers to update
Implementation
@override
void notify() {
delegated.source.notify();
}