ScopedRegistrationOf.~this

Destroy this scoped registration, detaching the underlying registration if it is still attached.

Finalizer caveat: this destructor touches another GC-managed object (the underlying Registration and its hap state). It is reliable for stack-allocated, struct-member and explicitly destroyed owners; for owners collected by the GC as class instances, the D specification does not guarantee that referenced objects are still valid during finalization. Call detach() at a deterministic lifecycle point and treat this destructor as a best-effort backstop.