feat(companion): add idle observability alias

src/companion/runtimeClient.ts

@@ -326,6 +326,10 @@ export class CompanionRuntimeClient {
     return this.pendingRequestCount > 0 || this.pendingEventWaitCount > 0;
   }
 
+  get idle(): boolean {
+    return !this.hasPendingWork;
+  }
+
   getPendingWorkSnapshot(): PendingWorkSnapshot {
     return {
       pendingRequestCount: this.pendingRequestCount,