feat(modbus-rtu): bind Transport mode on options/DTO/factory (string-enum guard)

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

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Contracts/ModbusDriverOptions.cs

@@ -130,6 +130,14 @@ public sealed class ModbusDriverOptions
     /// </summary>
     public MelsecFamily MelsecSubFamily { get; init; } = MelsecFamily.Q_L_iQR;
 
+    /// <summary>
+    ///     Wire transport selector. <see cref="ModbusTransportMode.Tcp"/> (default) is the
+    ///     historical Modbus TCP/MBAP framing. <see cref="ModbusTransportMode.RtuOverTcp"/>
+    ///     frames Modbus RTU PDUs (CRC16, no MBAP header) over the same TCP socket — for
+    ///     serial-to-Ethernet gateways that bridge RS-485 without re-encapsulating to MBAP.
+    /// </summary>
+    public ModbusTransportMode Transport { get; init; } = ModbusTransportMode.Tcp;
+
     /// <summary>
     ///     When <c>true</c>, the driver suppresses redundant writes: if the most recent
     ///     successful write to a tag carried value V and a new write of V arrives, the second