AsyncSignal<T> class abstract interface

Interface for reactive signals that manage async state transitions.

AsyncSignal wraps an AsyncSource and provides a reactive interface to async operations, automatically managing state transitions and providing convenient access to the current async state.

Example:

AsyncSignal<String> signal = AsyncSignal.fromFuture(
  Future.delayed(Duration(seconds: 1), () => 'Hello')
);

Effect(() {
  if (signal.value.isSuccess) {
    print('Data: ${signal.data}');
  }
});