feat(batch11): complete filestore init feature and test port

dotnet/tests/ZB.MOM.NatsNet.Server.Tests/ImplBacklog/ConcurrencyTests1.Impltests.cs

@@ -81,6 +81,59 @@ public sealed partial class ConcurrencyTests1
         });
     }
 
+    [Fact] // T:2427
+    public void NoRaceJetStreamFileStoreKeyFileCleanup_ShouldSucceed()
+    {
+        WithStore((_, root) =>
+        {
+            var msgDir = Path.Combine(root, FileStoreDefaults.MsgDir);
+            Directory.CreateDirectory(msgDir);
+            var perm = UnixFileMode.UserRead | UnixFileMode.UserWrite;
+
+            var errors = new ConcurrentQueue<Exception>();
+            Parallel.For(0, 300, i =>
+            {
+                var payload = BitConverter.GetBytes(i);
+                var keyFile = Path.Combine(msgDir, string.Format(FileStoreDefaults.KeyScan, (uint)(i + 1)));
+                var err = JetStreamFileStore.WriteAtomically(keyFile, payload, perm, sync: true);
+                if (err != null)
+                    errors.Enqueue(err);
+            });
+
+            errors.ShouldBeEmpty();
+            var keyFiles = Directory.GetFiles(msgDir, "*.key");
+            keyFiles.Length.ShouldBe(300);
+
+            foreach (var key in keyFiles.Skip(1))
+                File.Delete(key);
+
+            Directory.GetFiles(msgDir, "*.key").Length.ShouldBe(1);
+            Directory.GetFiles(msgDir, "*.tmp").ShouldBeEmpty();
+        });
+    }
+
+    [Fact] // T:2447
+    public void NoRaceEncodeConsumerStateBug_ShouldSucceed()
+    {
+        for (var i = 0; i < 5_000; i++)
+        {
+            var pending = new Pending
+            {
+                Sequence = 1,
+                Timestamp = DateTimeOffset.UtcNow.AddSeconds(1).ToUnixTimeSeconds() * 1_000_000_000L,
+            };
+            var state = new ConsumerState
+            {
+                Delivered = new SequencePair { Consumer = 1, Stream = 1 },
+                Pending = new Dictionary<ulong, Pending> { [1] = pending },
+            };
+
+            var encoded = StoreParity.EncodeConsumerState(state);
+            var (_, err) = JetStreamFileStore.DecodeConsumerState(encoded);
+            err.ShouldBeNull();
+        }
+    }
+
     private static void WithStore(Action<JetStreamFileStore, string> action, StreamConfig? cfg = null)
     {
         var root = NewRoot();