Generalize null/empty response handling with SendOrThrowAsync<TResponse, TException>, allowing custom exceptions via a factory delegate. SendOrNotFoundAsync now wraps this method for NotFoundException. Improves type safety, flexibility, and XML docs; avoids treating strings as collections.
Introduced MediatorExtensions with SendOrNotFoundAsync methods to enforce non-null and non-empty responses from MediatR requests. These extensions throw NotFoundException when responses are null or empty, centralizing not-found logic and improving error handling.
