feat(companion): expose pending request observability

src/companion/runtimeClient.ts

@@ -302,6 +302,10 @@ export class CompanionRuntimeClient {
     return this.eventHandlers.size;
   }
 
+  get pendingRequestCount(): number {
+    return this.pending.size;
+  }
+
   async connect(): Promise<void> {
     if (this.connected) {
       return;