AsyncEffectHandler

Handles an Effect that shouldn't block the transition that produced it — typically network calls. Unlike EffectHandler, this doesn't run as part of the current transition and doesn't produce an EffectResult: it runs independently (cancelled if the chat goes idle, see ChatWorkers in telek's implementation), and whatever Event it returns re-enters the FSM as its own, later transition — handled by StateDispatcher's transition(state, event) overload.

Register with EffectRegistry.registerAsync, not EffectRegistry.register — an effect class should be registered as one or the other, never both.