feat: complete jetstream deep operational parity closure

tests/NATS.Server.Tests/JetStreamInternalClientTests.cs

@@ -1,5 +1,7 @@
 using Microsoft.Extensions.Logging.Abstractions;
 using NATS.Server.Configuration;
+using NATS.Server.JetStream;
+using System.Reflection;
 
 namespace NATS.Server.Tests;
 
@@ -28,5 +30,9 @@ public class JetStreamInternalClientTests
         server.JetStreamInternalClient.ShouldNotBeNull();
         server.JetStreamInternalClient!.Kind.ShouldBe(ClientKind.JetStream);
         server.JetStreamInternalClient.Account?.Name.ShouldBe("$SYS");
+
+        var serviceField = typeof(NatsServer).GetField("_jetStreamService", BindingFlags.Instance | BindingFlags.NonPublic);
+        serviceField.ShouldNotBeNull();
+        (serviceField!.GetValue(server) as JetStreamService).ShouldNotBeNull();
     }
 }