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>

src/Drivers/Cli/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli/Commands/SubscribeCommand.cs

@@ -53,6 +53,7 @@ public sealed class SubscribeCommand : ModbusCommandBase
     public override async ValueTask ExecuteAsync(IConsole console)
     {
         ConfigureLogging();
+        ValidateEndpoint();
         var ct = console.RegisterCancellationHandler();
 
         var tagName = ReadCommand.SynthesiseTagName(Region, Address, DataType);
@@ -69,6 +70,9 @@ public sealed class SubscribeCommand : ModbusCommandBase
         var options = BuildOptions([tag]);
 
         await using var driver = new ModbusDriver(options, DriverInstanceId);
+        // Driver.Modbus.Cli-004: serialize console writes from the PollGroupEngine background
+        // thread so overlapping poll ticks can't interleave partial lines.
+        var writeLock = new object();
         ISubscriptionHandle? handle = null;
         try
         {
@@ -78,10 +82,26 @@ public sealed class SubscribeCommand : ModbusCommandBase
             // analyzer flags it + IConsole is the testable abstraction).
             driver.OnDataChange += (_, e) =>
             {
-                var line = $"[{DateTime.UtcNow:HH:mm:ss.fff}] " +
-                    $"{e.FullReference} = {SnapshotFormatter.FormatValue(e.Snapshot.Value)} " +
-                    $"({SnapshotFormatter.FormatStatus(e.Snapshot.StatusCode)})";
-                console.Output.WriteLine(line);
+                // Driver.Modbus.Cli-004: swallow + log write failures so a transient stdout
+                // error (closed pipe, IO exception on a redirected stream) cannot tear down
+                // the poll-engine background loop. Without this guard the unhandled
+                // exception would fault the long-running subscribe.
+                try
+                {
+                    var line = $"[{DateTime.UtcNow:HH:mm:ss.fff}] " +
+                        $"{e.FullReference} = {SnapshotFormatter.FormatValue(e.Snapshot.Value)} " +
+                        $"({SnapshotFormatter.FormatStatus(e.Snapshot.StatusCode)})";
+                    lock (writeLock)
+                    {
+                        console.Output.WriteLine(line);
+                    }
+                }
+                catch (Exception ex)
+                {
+                    Serilog.Log.Logger.Warning(ex,
+                        "SubscribeCommand: console write failed for {Tag}; continuing poll loop.",
+                        e.FullReference);
+                }
             };
 
             handle = await driver.SubscribeAsync([tagName], TimeSpan.FromMilliseconds(IntervalMs), ct);