SD-M2d: operator-channel's offered and closed are on the router's stream asks, mesh.stream.<holder>.event.*

The messenger keeps them in its own stream asks (its manifest's streams, design 55 § 11), so they ride that
stream's subjects, as the checker's verdict does.

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

ts/src/operator-channel.ts

@@ -51,11 +51,11 @@ export function refusedHolderSubject(holder: string): string {
 }
 
 export function offeredHolderSubject(holder: string): string {
-  return "mesh.mod." + holder + ".event.offered";
+  return "mesh.stream." + holder + ".event.offered";
 }
 
 export function closedHolderSubject(holder: string): string {
-  return "mesh.mod." + holder + ".event.closed";
+  return "mesh.stream." + holder + ".event.closed";
 }
 
 export interface Ask {