Single-type-argument forms of AddAggregate / AddSaga. The concrete class
 already names its state/command/event types on its Aggregate<,,> / Saga<,,>
 base, so registration repeats none of them:

     .AddAggregate()
     .AddSaga(create: sp => new QuotaSaga(...), startOn: e => ...)   // TSaga inferred

 Reflection runs once per registration, while the host is being composed —
 nothing on the message path. The four-type-argument instance overloads remain
 for classes that acquire the base generically.