Return the hold offer() took

src/held-messages.ts

@@ -124,13 +124,15 @@ export class HeldMessages {
 		listeners: number,
 		build: (hold: MessageHold) => T,
 		emit: (message: T) => boolean,
-	): void {
+	): MessageHold {
 		const hold = this.hold(pduObjs, listeners);
 		const message = build(hold);
 
 		this.offered.set(message, hold);
 
 		if (!emit(message)) hold.release();
+
+		return hold;
 	}
 
 	/** One listener gave up on a message; the last one to do so is what releases it. */