feat(modbus-rtu): add Transport selector to the AdminUI Modbus driver form

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/Forms/ModbusDriverForm.razor

@@ -27,6 +27,16 @@
                     }
                 </InputSelect>
             </div>
+            <div class="col-md-3">
+                <label class="form-label">Transport</label>
+                <InputSelect @bind-Value="_form.Transport" @bind-Value:after="EmitAsync" class="form-select form-select-sm">
+                    @foreach (var e in Enum.GetValues<ModbusTransportMode>())
+                    {
+                        <option value="@e">@e</option>
+                    }
+                </InputSelect>
+                <div class="form-text">RtuOverTcp = talk raw RTU frames to a serial→Ethernet gateway; must match the gateway's mode.</div>
+            </div>
             <div class="col-md-3">
                 <label class="form-label">MELSEC sub-family</label>
                 <InputSelect @bind-Value="_form.MelsecSubFamily" @bind-Value:after="EmitAsync" class="form-select form-select-sm">
@@ -290,6 +300,9 @@
         public ModbusFamily Family { get; set; } = ModbusFamily.Generic;
         public MelsecFamily MelsecSubFamily { get; set; } = MelsecFamily.Q_L_iQR;
 
+        // Wire transport (Tcp = Modbus/TCP MBAP; RtuOverTcp = RTU framing over a serial→Ethernet gateway)
+        public ModbusTransportMode Transport { get; set; } = ModbusTransportMode.Tcp;
+
         // Transport flags
         public bool AutoReconnect { get; set; } = true;
         public int IdleDisconnectTimeoutSeconds { get; set; } = 0;
@@ -337,6 +350,7 @@
             TimeoutSeconds = (int)o.Timeout.TotalSeconds,
             Family = o.Family,
             MelsecSubFamily = o.MelsecSubFamily,
+            Transport = o.Transport,
             AutoReconnect = o.AutoReconnect,
             IdleDisconnectTimeoutSeconds = o.IdleDisconnectTimeout.HasValue ? (int)o.IdleDisconnectTimeout.Value.TotalSeconds : 0,
             MaxRegistersPerRead = o.MaxRegistersPerRead,
@@ -387,6 +401,7 @@
             MaxReadGap = (ushort)Math.Clamp(MaxReadGap, 0, 65535),
             Family = Family,
             MelsecSubFamily = MelsecSubFamily,
+            Transport = Transport,
             WriteOnChangeOnly = WriteOnChangeOnly,
             AutoReconnect = AutoReconnect,
             KeepAlive = new ModbusKeepAliveOptions

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/ModbusDriverFormModelTests.cs

@@ -61,4 +61,15 @@ public sealed class ModbusDriverFormModelTests
         json.ShouldContain("\"family\":\"MELSEC\"");           // enum-as-name (not a number), camelCase key
         json.ShouldNotContain("\"family\":0", Case.Sensitive); // never the numeric enum form
     }
+
+    [Fact]
+    public void Round_trip_preserves_Transport_mode()
+    {
+        var form = new ModbusDriverForm.FormModel { Transport = ModbusTransportMode.RtuOverTcp };
+        var json = JsonSerializer.Serialize(form.ToOptions(), JsonOpts);
+        var back = ModbusDriverForm.FormModel.FromOptions(
+            JsonSerializer.Deserialize<ModbusDriverOptions>(json, JsonOpts)!);
+        back.Transport.ShouldBe(ModbusTransportMode.RtuOverTcp);
+        json.ShouldContain("\"transport\":\"RtuOverTcp\""); // name string, never a number
+    }
 }