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/ProbeCommandTests.cs

@@ -0,0 +1,60 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli.Commands;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli.Tests;
+
+/// <summary>
+///     Covers <see cref="ProbeCommand.ComputeVerdict"/> — the headline-string helper that
+///     combines the driver-side <see cref="DriverState"/> with the probe snapshot's OPC UA
+///     <see cref="DataValueSnapshot.StatusCode"/> so the operator never sees the previous
+///     contradictory pair (`Health: Healthy` above a `Status: Bad...` snapshot line — see
+///     Driver.Modbus.Cli-006).
+/// </summary>
+[Trait("Category", "Unit")]
+public sealed class ProbeCommandTests
+{
+    [Fact]
+    public void ComputeVerdict_returns_OK_when_state_is_Healthy_and_status_is_Good()
+    {
+        var verdict = ProbeCommand.ComputeVerdict(DriverState.Healthy, statusCode: 0x00000000u);
+
+        verdict.ShouldContain("OK");
+    }
+
+    [Theory]
+    [InlineData(DriverState.Faulted)]
+    [InlineData(DriverState.Reconnecting)]
+    [InlineData(DriverState.Unknown)]
+    public void ComputeVerdict_returns_FAIL_when_driver_state_is_not_Healthy(DriverState state)
+    {
+        var verdict = ProbeCommand.ComputeVerdict(state, statusCode: 0x00000000u);
+
+        verdict.ShouldContain("FAIL");
+    }
+
+    [Theory]
+    [InlineData(0x80050000u)] // BadCommunicationError
+    [InlineData(0x800A0000u)] // BadTimeout
+    [InlineData(0x80740000u)] // BadTypeMismatch
+    [InlineData(0x80000000u)] // generic Bad
+    public void ComputeVerdict_returns_FAIL_when_snapshot_status_is_Bad_even_if_driver_state_Healthy(uint statusCode)
+    {
+        // Driver.Modbus.Cli-006: a successful InitializeAsync sets DriverState.Healthy, but
+        // the FC03 probe read may still fail (snapshot.StatusCode != Good). Previously the
+        // headline reported Healthy while the snapshot line below showed Bad. The verdict
+        // must reflect the actual probe-read outcome.
+        var verdict = ProbeCommand.ComputeVerdict(DriverState.Healthy, statusCode);
+
+        verdict.ShouldContain("FAIL");
+    }
+
+    [Fact]
+    public void ComputeVerdict_returns_DEGRADED_for_uncertain_status_with_healthy_driver()
+    {
+        var verdict = ProbeCommand.ComputeVerdict(DriverState.Healthy, statusCode: 0x40000000u);
+
+        verdict.ShouldContain("DEGRADED");
+    }
+}