chore: organize solution into module folders (Core/Server/Drivers/Client/Tooling)

Group all 69 projects into category subfolders under src/ and tests/ so the
Rider Solution Explorer mirrors the module structure. Folders: Core, Server,
Drivers (with a nested Driver CLIs subfolder), Client, Tooling.

- Move every project folder on disk with git mv (history preserved as renames).
- Recompute relative paths in 57 .csproj files: cross-category ProjectReferences,
  the lib/ HintPath+None refs in Driver.Historian.Wonderware, and the external
  mxaccessgw refs in Driver.Galaxy and its test project.
- Rebuild ZB.MOM.WW.OtOpcUa.slnx with nested solution folders.
- Re-prefix project paths in functional scripts (e2e, compliance, smoke SQL,
  integration, install).

Build green (0 errors); unit tests pass. Docs left for a separate pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -0,0 +1,45 @@
+using Shouldly;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.IntegrationTests.Mitsubishi;
+
+/// <summary>
+///     End-to-end smoke against the MELSEC <c>mitsubishi.json</c> pymodbus profile (or a real
+///     MELSEC QJ71MT91 / iQ-R / FX5U when <c>MODBUS_SIM_ENDPOINT</c> points at one). Drives
+///     the full <see cref="ModbusDriver"/> + real <see cref="ModbusTcpTransport"/> stack.
+///     Success proves the driver initializes against the MELSEC sim, writes a known value,
+///     and reads it back — the baseline every Mitsubishi-specific test (PR 59+) builds on.
+/// </summary>
+[Collection(ModbusSimulatorCollection.Name)]
+[Trait("Category", "Integration")]
+[Trait("Device", "Mitsubishi")]
+public sealed class MitsubishiSmokeTests(ModbusSimulatorFixture sim)
+{
+    [Fact]
+    public async Task Mitsubishi_roundtrip_write_then_read_of_holding_register()
+    {
+        if (sim.SkipReason is not null) Assert.Skip(sim.SkipReason);
+        if (!string.Equals(Environment.GetEnvironmentVariable("MODBUS_SIM_PROFILE"), "mitsubishi",
+                StringComparison.OrdinalIgnoreCase))
+        {
+            Assert.Skip("MODBUS_SIM_PROFILE != mitsubishi — skipping.");
+        }
+
+        var options = MitsubishiProfile.BuildOptions(sim.Host, sim.Port);
+        await using var driver = new ModbusDriver(options, driverInstanceId: "melsec-smoke");
+        await driver.InitializeAsync(driverConfigJson: "{}", TestContext.Current.CancellationToken);
+
+        var writeResults = await driver.WriteAsync(
+            [new(FullReference: "Smoke_HReg200", Value: (short)MitsubishiProfile.SmokeHoldingValue)],
+            TestContext.Current.CancellationToken);
+        writeResults.Count.ShouldBe(1);
+        writeResults[0].StatusCode.ShouldBe(0u, "write must succeed against the MELSEC pymodbus profile");
+
+        var readResults = await driver.ReadAsync(
+            ["Smoke_HReg200"],
+            TestContext.Current.CancellationToken);
+        readResults.Count.ShouldBe(1);
+        readResults[0].StatusCode.ShouldBe(0u);
+        readResults[0].Value.ShouldBe((short)MitsubishiProfile.SmokeHoldingValue);
+    }
+}