Phase 3 PR 58 -- Mitsubishi MELSEC pymodbus profile + smoke integration test. Adds tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Pymodbus/mitsubishi.json modelling a representative MELSEC Modbus Device Assignment block: D0..D1023 -> HR[0..1023], M-relay marker at coil 512 (cell 32) and X-input marker at DI 528 (cell 33). Covers the canonical MELSEC quirks from docs/v2/mitsubishi.md: D0 fingerprint at HR[0]=0x1234 so clients can verify the assignment parameter block is in effect, scratch HR 200..209 mirroring dl205/s7_1500/standard scratch range for uniform smoke tests, Float32 1.5f at HR[100..101] in CDAB word order (HR[100]=0, HR[101]=0x3FC0) -- same as DL260, OPPOSITE of S7 ABCD, confirms MELSEC-family driver profile default must be ByteOrder.WordSwap. Int32 0x12345678 CDAB at HR[300..301]. D10 = binary 1234 (0x04D2) proves MELSEC is BINARY-by-default (opposite of DL205 BCD-by-default quirk) -- reading D10 with Bcd16 data type would throw InvalidDataException on nibble 0xD. M-relay marker cell moved to address 32 (coil 512) to avoid shared-block collision with D0 uint16 marker at cell 0; pymodbus shared-blocks=true semantics allow only one type per cell index, so Modbus-coil-0 can't coexist with Modbus-HR-0 on the same sim. Same pattern we applied to dl205 profile (X-input bank at cell 1, not cell 0, to coexist with V0 marker). Adds Mitsubishi/ test directory with MitsubishiProfile.cs (SmokeHoldingRegister=200, SmokeHoldingValue=7890, BuildOptions with probe-disabled + 2s timeout) and MitsubishiSmokeTests.cs (Mitsubishi_roundtrip_write_then_read_of_holding_register single fact that writes 7890 at HR[200] then reads back, gated on MODBUS_SIM_PROFILE=mitsubishi). csproj copies Mitsubishi/** as PreserveNewest. Per-model differences (FX5U firmware gate, QJ71MT91 FC22/23 absence, FX/iQ-F octal vs Q/L/iQ-R hex X-addressing) are handled in the MelsecAddress helper (PR 59) + per-model test classes (PR 60). Verified: smoke 1/1 passes against live mitsubishi sim. Prior S7 tests 4/4 still green when swapped back. Modbus.Tests unit suite 143/143.

tests/ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests/Mitsubishi/MitsubishiProfile.cs

@@ -0,0 +1,43 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests.Mitsubishi;
+
+/// <summary>
+///     Tag map for the Mitsubishi MELSEC device class with a representative Modbus Device
+///     Assignment block mapping D0..D1023 → HR[0..1023]. Mirrors the behaviors in
+///     <c>mitsubishi.json</c> pymodbus profile and <c>docs/v2/mitsubishi.md</c>.
+/// </summary>
+/// <remarks>
+///     MELSEC Modbus sites all have *different* device-assignment parameter blocks; this profile
+///     models the conventional default. Per-model differences (FX5U needs firmware ≥ 1.060 for
+///     Modbus server; QJ71MT91 lacks FC22/FC23; FX/iQ-F use octal X/Y while Q/L/iQ-R use hex)
+///     are handled in <see cref="MelsecAddress"/> (PR 59) and the per-model test files.
+/// </remarks>
+public static class MitsubishiProfile
+{
+    /// <summary>
+    ///     Scratch HR the smoke test writes + reads. Address 200 mirrors the
+    ///     dl205/s7_1500/standard scratch range so one smoke test pattern works across every
+    ///     device profile the simulator supports.
+    /// </summary>
+    public const ushort SmokeHoldingRegister = 200;
+
+    /// <summary>Value the smoke test writes then reads back.</summary>
+    public const short SmokeHoldingValue = 7890;
+
+    public static ModbusDriverOptions BuildOptions(string host, int port) => new()
+    {
+        Host = host,
+        Port = port,
+        UnitId = 1,
+        Timeout = TimeSpan.FromSeconds(2),
+        Tags =
+        [
+            new ModbusTagDefinition(
+                Name: "Smoke_HReg200",
+                Region: ModbusRegion.HoldingRegisters,
+                Address: SmokeHoldingRegister,
+                DataType: ModbusDataType.Int16,
+                Writable: true),
+        ],
+        Probe = new ModbusProbeOptions { Enabled = false },
+    };
+}