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>

docs/Driver.Modbus.Cli.md

@@ -122,6 +122,14 @@ gives plausible values is the correct one for that device.
 
 ## v2 addressing grammar
 
+> **CLI scope:** the `read` / `write` / `subscribe` commands accept only
+> the structured `--region` + `--address` + `--type` triple. The
+> address-string grammar below is a **`DriverConfig` JSON** feature
+> consumed by the driver itself; it is not reachable from this CLI's
+> flags. To experiment with it via the CLI, use the structured flags;
+> to deploy spreadsheets as-is, hand-author a `DriverConfig` and run
+> the server.
+
 The driver accepts the industry-standard tag-address grammar so you can
 paste tag spreadsheets from Wonderware / Kepware / Ignition without
 per-row manual translation. Full reference + grammar rules: