fix: complete retail parity stability pass

tests/AcDream.Core.Net.Tests/Transport/OutboundReliableTransportTests.cs

@@ -392,6 +392,29 @@ public sealed class OutboundReliableTransportTests
         Assert.Equal(5u, wrapQueue.AckWatermark);
     }
 
+    [Fact]
+    public void NewerAckOvertakingQueuedNak_SuppressesStaleEncryptedResend()
+    {
+        (OutboundFlowQueue queue, _, _, TransportStats stats,
+            List<byte[]> sent) = CreateQueue();
+        queue.SendGameMessage(MakeMessage(2), GameMessageGroup.UIQueue);
+        queue.SendGameMessage(MakeMessage(3), GameMessageGroup.UIQueue);
+        queue.SendGameMessage(MakeMessage(4), GameMessageGroup.UIQueue);
+
+        // The NAK for seq 2 is queued first. Before the frame sweep, a later
+        // cumulative ACK proves the server has already advanced through 3.
+        Nak(queue, 2u);
+        queue.OnAckSequence(3u);
+        sent.Clear();
+
+        queue.TransmitPendingResends();
+
+        Assert.Empty(sent);
+        Assert.Equal(0, stats.ResendsSent);
+        Assert.Equal(2, queue.CacheDepth); // watermark itself + newer seq 4
+        Assert.Equal(0, queue.PendingResendCount);
+    }
+
     // =====================================================================
     // Conformance against the N0 ACE-behaviour double
     // =====================================================================