feat(companion): expose runtime event subscription count

src/companion/runtimeClient.ts

@@ -298,6 +298,10 @@ export class CompanionRuntimeClient {
     return this.ws?.readyState === WebSocket.OPEN;
   }
 
+  get eventSubscriptionCount(): number {
+    return this.eventHandlers.size;
+  }
+
   async connect(): Promise<void> {
     if (this.connected) {
       return;