Event Invoker
Sealed marker interface for all event invocation strategies.
The event system compiles or constructs concrete invokers that know how to call specific handler methods. Two primary specializations exist:
InstanceEventInvoker for handlers that require a receiver instance.
StaticEventInvoker for handlers implemented as static methods.
The sealed hierarchy allows the dispatcher to pattern-match on the invoker type when performing calls, while still treating all invokers uniformly at the type level.
This interface is internal and not exposed through the public API.