fix(driver-modbus-cli): resolve Low code-review findings (Driver.Modbus.Cli-003,004,005,006,007,008)

- Driver.Modbus.Cli-003: ModbusCommandBase.ValidateEndpoint rejects
  --port outside 1..65535, non-positive --timeout-ms, and --unit-id
  outside 1..247.
- Driver.Modbus.Cli-004: wrapped SubscribeCommand's OnDataChange handler
  body in a try/catch (warn-and-swallow) and serialised the console
  write through a lock.
- Driver.Modbus.Cli-005: Probe / Read / Write now catch the
  cancellation-during-init OperationCanceledException and print
  'Cancelled.' instead of dumping a stack trace.
- Driver.Modbus.Cli-006: ProbeCommand.ComputeVerdict derives the headline
  from BOTH the driver state and the probe snapshot's OPC UA quality
  class so the headline can't disagree with the wire result.
- Driver.Modbus.Cli-007: docs/Driver.Modbus.Cli.md carries an explicit
  'CLI scope' callout — the address-string grammar is a DriverConfig
  JSON feature; the CLI takes the structured triple only.
- Driver.Modbus.Cli-008: pinned BuildOptions, ValidateEndpoint, the
  region-validation guards, ComputeVerdict, and the cancellation-during-
  initialize paths.

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

tests/Drivers/Cli/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli.Tests/WriteCommandRegionValidationTests.cs

@@ -0,0 +1,63 @@
+using CliFx.Infrastructure;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli.Commands;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli.Tests;
+
+/// <summary>
+///     Covers the branch validation inside <see cref="WriteCommand.ExecuteAsync"/>:
+///     1. Driver.Modbus.Cli-002 — write to <see cref="ModbusRegion.Coils"/> must use
+///        <c>--type Bool</c>.
+///     2. Read-only regions (DiscreteInputs / InputRegisters) reject any write.
+///     The actual driver call is never reached for these guard cases — they throw a
+///     <see cref="CliFx.Exceptions.CommandException"/> before the driver is constructed,
+///     so we can exercise <c>ExecuteAsync</c> against an unreachable host.
+/// </summary>
+[Trait("Category", "Unit")]
+public sealed class WriteCommandRegionValidationTests
+{
+    [Theory]
+    [InlineData(ModbusRegion.DiscreteInputs, ModbusDataType.Bool, "0")]
+    [InlineData(ModbusRegion.InputRegisters, ModbusDataType.UInt16, "1")]
+    public async Task ExecuteAsync_rejects_read_only_regions(
+        ModbusRegion region, ModbusDataType type, string value)
+    {
+        var sut = new WriteCommand
+        {
+            // Host is required, but the guard fires before any socket use.
+            Host = "127.0.0.1",
+            Region = region,
+            Address = 0,
+            DataType = type,
+            Value = value,
+        };
+        using var console = new FakeInMemoryConsole();
+
+        await Should.ThrowAsync<CliFx.Exceptions.CommandException>(
+            async () => await sut.ExecuteAsync(console));
+    }
+
+    [Theory]
+    [InlineData(ModbusDataType.UInt16)]
+    [InlineData(ModbusDataType.Int16)]
+    [InlineData(ModbusDataType.Float32)]
+    [InlineData(ModbusDataType.Int32)]
+    public async Task ExecuteAsync_rejects_non_Bool_type_for_Coils_region(ModbusDataType type)
+    {
+        var sut = new WriteCommand
+        {
+            Host = "127.0.0.1",
+            Region = ModbusRegion.Coils,
+            Address = 5,
+            DataType = type,
+            Value = "42",
+        };
+        using var console = new FakeInMemoryConsole();
+
+        var ex = await Should.ThrowAsync<CliFx.Exceptions.CommandException>(
+            async () => await sut.ExecuteAsync(console));
+        ex.Message.ShouldContain("Coils");
+        ex.Message.ShouldContain("Bool");
+    }
+}