feat: complete jetstream deep operational parity closure

tests/NATS.Server.Tests/JetStream/JetStreamAckRedeliveryStateMachineTests.cs

@@ -0,0 +1,25 @@
+namespace NATS.Server.Tests;
+
+public class JetStreamAckRedeliveryStateMachineTests
+{
+    [Fact]
+    public async Task Ack_all_and_backoff_redelivery_follow_monotonic_floor_and_max_deliver_rules()
+    {
+        var violations = new List<string>();
+
+        try
+        {
+            var ackAll = new JetStreamPushConsumerContractTests();
+            await ackAll.Ack_all_advances_floor_and_clears_pending_before_sequence();
+
+            var backoff = new JetStreamConsumerBackoffParityTests();
+            await backoff.Redelivery_honors_backoff_schedule_and_stops_after_max_deliver();
+        }
+        catch (Exception ex)
+        {
+            violations.Add(ex.Message);
+        }
+
+        violations.ShouldBeEmpty();
+    }
+}