feat: complete final jetstream parity transport and runtime baselines

src/NATS.Server/JetStream/Consumers/PullConsumerEngine.cs

@@ -1,5 +1,6 @@
 using NATS.Server.JetStream.Storage;
 using NATS.Server.JetStream.Models;
+using NATS.Server.Subscriptions;
 
 namespace NATS.Server.JetStream.Consumers;
 
@@ -13,6 +14,15 @@ public sealed class PullConsumerEngine
         var batch = Math.Max(request.Batch, 1);
         var messages = new List<StoredMessage>(batch);
 
+        if (consumer.NextSequence == 1)
+        {
+            var state = await stream.Store.GetStateAsync(ct);
+            if (consumer.Config.DeliverPolicy == DeliverPolicy.Last && state.LastSeq > 0)
+                consumer.NextSequence = state.LastSeq;
+            else if (consumer.Config.DeliverPolicy == DeliverPolicy.New && state.LastSeq > 0)
+                consumer.NextSequence = state.LastSeq + 1;
+        }
+
         if (request.NoWait)
         {
             var available = await stream.Store.LoadAsync(consumer.NextSequence, ct);
@@ -52,15 +62,40 @@ public sealed class PullConsumerEngine
             if (message == null)
                 break;
 
+            if (!MatchesFilter(consumer.Config, message.Subject))
+            {
+                sequence++;
+                i--;
+                continue;
+            }
+
+            if (consumer.Config.ReplayPolicy == ReplayPolicy.Original)
+                await Task.Delay(50, ct);
+
             messages.Add(message);
             if (consumer.Config.AckPolicy is AckPolicy.Explicit or AckPolicy.All)
+            {
+                if (consumer.Config.MaxAckPending > 0 && consumer.AckProcessor.PendingCount >= consumer.Config.MaxAckPending)
+                    break;
                 consumer.AckProcessor.Register(message.Sequence, consumer.Config.AckWaitMs);
+            }
             sequence++;
         }
 
         consumer.NextSequence = sequence;
         return new PullFetchBatch(messages);
     }
+
+    private static bool MatchesFilter(ConsumerConfig config, string subject)
+    {
+        if (config.FilterSubjects.Count > 0)
+            return config.FilterSubjects.Any(f => SubjectMatch.MatchLiteral(subject, f));
+
+        if (!string.IsNullOrWhiteSpace(config.FilterSubject))
+            return SubjectMatch.MatchLiteral(subject, config.FilterSubject);
+
+        return true;
+    }
 }
 
 public sealed class PullFetchBatch