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/ModbusCommandBase.cs

@@ -1,4 +1,5 @@
 using CliFx.Attributes;
+using CliFx.Exceptions;
 using ZB.MOM.WW.OtOpcUa.Driver.Cli.Common;
 
 namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli;
@@ -57,4 +58,33 @@ public abstract class ModbusCommandBase : DriverCommandBase
     ///     multiple endpoints in parallel can distinguish the logs.
     /// </summary>
     protected string DriverInstanceId => $"modbus-cli-{Host}:{Port}";
+
+    /// <summary>
+    ///     Driver.Modbus.Cli-003: validate the endpoint flags at parse time so the operator
+    ///     gets a clear CliFx error instead of an opaque socket / argument exception thrown
+    ///     deep inside the driver. Ranges:
+    ///     <list type="bullet">
+    ///       <item><c>--port</c>: 1..65535 (IANA TCP port space, excludes the
+    ///         "any" sentinel 0 and rejects negative / overflowed values).</item>
+    ///       <item><c>--timeout-ms</c>: strictly positive — a non-positive
+    ///         <see cref="TimeSpan"/> would propagate as an immediate-timeout into the
+    ///         driver and surface as a confusing TimeoutException.</item>
+    ///       <item><c>--unit-id</c>: 1..247 — the Modbus spec unicast unit-id range.
+    ///         0 is the broadcast address and not valid for read/write requests; 248-255
+    ///         are reserved. (Documented in <c>docs/Driver.Modbus.Cli.md</c>.)</item>
+    ///     </list>
+    /// </summary>
+    protected void ValidateEndpoint()
+    {
+        if (Port < 1 || Port > 65535)
+            throw new CommandException(
+                $"--port must be in 1..65535 (got {Port}).");
+        if (TimeoutMs <= 0)
+            throw new CommandException(
+                $"--timeout-ms must be strictly positive (got {TimeoutMs}).");
+        if (UnitId < 1 || UnitId > 247)
+            throw new CommandException(
+                $"--unit-id must be in 1..247 per the Modbus spec (got {UnitId}); " +
+                $"0 is the broadcast address, 248-255 are reserved.");
+    }
 }