task6(batch39): implement shutdown and signal flow paths

dotnet/tests/ZB.MOM.NatsNet.Server.Tests/ImplBacklog/RouteHandlerTests.cs

@@ -6,6 +6,30 @@ namespace ZB.MOM.NatsNet.Server.Tests.ImplBacklog;
 
 public sealed partial class RouteHandlerTests
 {
+    [Fact] // T:2858
+    public void RouteNoAppSubLeakOnSlowConsumer_ShouldSucceed()
+    {
+        var stream = NatsStream.Create(
+            new Account { Name = "A" },
+            new StreamConfig { Name = "S", Subjects = ["route.>"] },
+            null,
+            null,
+            null,
+            null);
+        stream.ShouldNotBeNull();
+
+        var consumer = NatsConsumer.Create(
+            stream!,
+            new ConsumerConfig { Durable = "D", DeliverSubject = "route.deliver", InactiveThreshold = TimeSpan.FromMilliseconds(10) },
+            ConsumerAction.CreateOrUpdate,
+            null);
+        consumer.ShouldNotBeNull();
+
+        consumer!.UpdateDeliveryInterest(localInterest: false).ShouldBeFalse();
+        consumer.DeleteNotActive();
+        consumer.IsClosed().ShouldBeTrue();
+    }
+
     [Fact] // T:2817
     public void RouteCloseTLSConnection_ShouldSucceed()
     {