Task #249 — Driver test-client CLIs: shared lib + Modbus CLI first

Mirrors the v1 otopcua-cli value prop (ad-hoc shell-level PLC validation) for
the Modbus-TCP driver, and lays down the shared scaffolding that AB CIP, AB
Legacy, S7, and TwinCAT CLIs will build on.

New projects:
  - src/ZB.MOM.WW.OtOpcUa.Driver.Cli.Common/ — DriverCommandBase (verbose
    flag + Serilog config) + SnapshotFormatter (single-tag + table +
    write-result renders with invariant-culture value formatting + OPC UA
    status-code shortnames + UTC-normalised timestamps).
  - src/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli/ — otopcua-modbus-cli executable.
    Commands: probe, read, write, subscribe. ModbusCommandBase carries the
    host/port/unit-id flags + builds ModbusDriverOptions with Probe.Enabled
    =false (CLI runs are one-shot; driver-internal keep-alive would race).

Commands + coverage:
  - probe              single FC03 + GetHealth() + pretty-print
  - read               region × address × type synth into one driver tag
  - write              same shape + --value parsed per --type
  - subscribe          polled-subscription stream until Ctrl+C

Tests (38 total):
  - 16 SnapshotFormatterTests covering: status-code shortnames, unknown
    codes fall back to hex, null value + timestamp placeholders, bool
    lowercase, float invariant culture, string quoting, write-result shape,
    aligned table columns, mismatched-length rejection, UTC normalisation.
  - 22 Modbus CLI tests:
      · ReadCommandTests.SynthesiseTagName (5 theory cases)
      · WriteCommandParseValueTests (17 cases: bool aliases, unknown rejected,
        Int16 bounds, UInt16/Bcd16 type, Float32/64 invariant culture,
        String passthrough, BitInRegister, Int32 MinValue, non-numeric reject)

Wiring:
  - ZB.MOM.WW.OtOpcUa.slnx grew 4 entries (2 src + 2 tests).
  - docs/Driver.Modbus.Cli.md — operator-facing runbook with examples per
    command + output format + typical workflows.

Regression: full-solution build clean; shared-lib tests 16/0, Modbus CLI tests
22/0.

Next up: repeat the pattern for AB CIP (shares ~40% more with Modbus via
libplctag), then AB Legacy, S7, TwinCAT. The shared base stays as-is unless
one of those exposes a gap the Modbus-first pass missed.

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

src/ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli/ModbusCommandBase.cs

@@ -0,0 +1,60 @@
+using CliFx.Attributes;
+using ZB.MOM.WW.OtOpcUa.Driver.Cli.Common;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus.Cli;
+
+/// <summary>
+///     Base for every Modbus CLI command. Carries the Modbus-TCP endpoint options
+///     (host / port / unit-id) on top of <see cref="DriverCommandBase"/>'s verbose + timeout
+///     + logging helpers, and exposes <see cref="BuildOptions"/> so each command can turn its
+///     parsed flags into a <see cref="ModbusDriverOptions"/> ready to hand to the driver ctor.
+/// </summary>
+public abstract class ModbusCommandBase : DriverCommandBase
+{
+    [CommandOption("host", 'h', Description = "Modbus-TCP server hostname or IP", IsRequired = true)]
+    public string Host { get; init; } = default!;
+
+    [CommandOption("port", 'p', Description = "Modbus-TCP port (default 502)")]
+    public int Port { get; init; } = 502;
+
+    [CommandOption("unit-id", 'U', Description = "Modbus unit / slave ID (1-247, default 1)")]
+    public byte UnitId { get; init; } = 1;
+
+    [CommandOption("timeout-ms", Description = "Per-PDU timeout in milliseconds (default 2000)")]
+    public int TimeoutMs { get; init; } = 2000;
+
+    [CommandOption("disable-reconnect", Description =
+        "Disable the built-in mid-transaction reconnect-and-retry. Matches the driver's " +
+        "AutoReconnect=false setting — use when diagnosing socket teardown behaviour.")]
+    public bool DisableAutoReconnect { get; init; }
+
+    /// <inheritdoc />
+    public override TimeSpan Timeout
+    {
+        get => TimeSpan.FromMilliseconds(TimeoutMs);
+        init { /* driven by TimeoutMs property; setter required to satisfy base's init contract */ }
+    }
+
+    /// <summary>
+    ///     Construct a <see cref="ModbusDriverOptions"/> with the endpoint fields this base
+    ///     collected + whatever <paramref name="tags"/> the subclass declares. Probe is
+    ///     disabled — CLI runs are one-shot, the probe loop would race the operator's
+    ///     command against its own keep-alive reads.
+    /// </summary>
+    protected ModbusDriverOptions BuildOptions(IReadOnlyList<ModbusTagDefinition> tags) => new()
+    {
+        Host = Host,
+        Port = Port,
+        UnitId = UnitId,
+        Timeout = Timeout,
+        AutoReconnect = !DisableAutoReconnect,
+        Tags = tags,
+        Probe = new ModbusProbeOptions { Enabled = false },
+    };
+
+    /// <summary>
+    ///     Short instance id used in Serilog output so operators running the CLI against
+    ///     multiple endpoints in parallel can distinguish the logs.
+    /// </summary>
+    protected string DriverInstanceId => $"modbus-cli-{Host}:{Port}";
+}