fix: FASS2 状态机与 UDP 枢纽审查项

等锁超时、全路径签名、无锁窗口不下发、Fault 终态可等待、Pass+机构不再短路、Alarm 不杀单、catch-up 停在未完成站；VehicleCode=0/重复车号拒绝注册，Hub 已运行时不抢监听口；FileLogger 空目录可写。

Co-authored-by: Cursor <cursoragent@cursor.com>

StandardScene.Magnetic.Tests/Protocol/Fass2UdpHubMultiCarTests.cs

@@ -57,6 +57,20 @@ namespace StandardScene.Magnetic.Tests.Protocol
             Assert.Equal((ulong)202, _car2.Reports[0].Task);
         }
 
+        [Fact]
+        public void EnsureStarted_NewPort_ReceivesOnNewPort()
+        {
+            var newPort = AllocateUdpPort();
+            Fass2UdpHub.EnsureStarted(newPort);
+            Thread.Sleep(150);
+
+            var frame = Fass2TestFrameBuilder.BuildStateFrame(1, 1, 88, 301);
+            using var sender = new UdpClient();
+            sender.Send(frame, frame.Length, new IPEndPoint(IPAddress.Loopback, newPort));
+            Assert.NotNull(_car1.WaitForAck());
+            Assert.Equal((ushort)88, _car1.Reports[_car1.Reports.Count - 1].Node.Node);
+        }
+
         [Fact]
         public void Hub_IgnoresUnregisteredCarCode()
         {
@@ -66,6 +80,31 @@ namespace StandardScene.Magnetic.Tests.Protocol
             Assert.Empty(_car2.Reports);
         }
 
+        [Fact]
+        public void Register_VehicleCodeZero_DoesNotReceiveState()
+        {
+            var zeroPort = AllocateUdpPort();
+            using var zero = new TestUdpCar(0, zeroPort);
+            Assert.False(Fass2UdpHub.Register(zero));
+
+            SendState(0, 2, 40, 0);
+            Thread.Sleep(200);
+            Assert.Empty(zero.Reports);
+        }
+
+        [Fact]
+        public void Register_DuplicateVehicleCode_KeepsFirstCar()
+        {
+            var dupPort = AllocateUdpPort();
+            using var dup = new TestUdpCar(1, dupPort);
+            Assert.False(Fass2UdpHub.Register(dup));
+
+            SendState(1, 2, 41, 401);
+            Assert.NotNull(_car1.WaitForAck());
+            Assert.Equal((ushort)41, _car1.Reports[_car1.Reports.Count - 1].Node.Node);
+            Assert.Empty(dup.Reports);
+        }
+
         public void Dispose()
         {
             Fass2UdpHub.Unregister(_car1);