Task #250 — AB CIP + AB Legacy test-client CLIs

Second + third of the four driver test clients. Both follow the same shape as
otopcua-modbus-cli (#249) and consume Driver.Cli.Common for DriverCommandBase +
SnapshotFormatter.

New projects:
  - src/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Cli/ — otopcua-abcip-cli.
    AbCipCommandBase carries gateway (ab://host[:port]/cip-path) + family
    (ControlLogix/CompactLogix/Micro800/GuardLogix) + timeout.
    Commands: probe, read, write, subscribe.
    Value parser covers every AbCipDataType atomic type (Bool, SInt..LInt,
    USInt..ULInt, Real, LReal, String, Dt); Structure writes refused as
    out-of-scope for the CLI.
  - src/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Cli/ — otopcua-ablegacy-cli.
    AbLegacyCommandBase carries gateway + plc-type (Slc500/MicroLogix/Plc5/
    LogixPccc) + timeout.
    Commands: probe (default address N7:0), read, write, subscribe.
    Value parser covers Bit, Int, Long, Float, AnalogInt, String, and the
    three sub-element types (TimerElement / CounterElement / ControlElement
    all land on int32 at the wire).

Tests (35 new, 73 cumulative across the driver CLI family):
  - AB CIP: 17 tests — ParseValue happy-paths for every Logix atomic type,
    failure cases (non-numeric / bool garbage), tag-name synthesis.
  - AB Legacy: 18 tests — ParseValue coverage (Bit / Int / AnalogInt / Long /
    Float / String / sub-elements), PCCC address round-trip in tag names
    including bit-within-word + sub-element syntax.

Docs:
  - docs/Driver.AbCip.Cli.md — family ↔ CIP-path cheat sheet + examples per
    command + typical workflows.
  - docs/Driver.AbLegacy.Cli.md — PCCC address primer (file letters → CLI
    --type) + known ab_server upstream gap cross-ref to #224 close-out.

Wiring:
  - ZB.MOM.WW.OtOpcUa.slnx grew 4 entries (2 src + 2 tests).

Full-solution build clean. `otopcua-abcip-cli --help` + `otopcua-ablegacy-cli
--help` verified end-to-end.

Next up (#251): S7 + TwinCAT CLIs, same pattern.

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

src/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Cli/Commands/ReadCommand.cs

@@ -0,0 +1,60 @@
+using CliFx.Attributes;
+using CliFx.Infrastructure;
+using ZB.MOM.WW.OtOpcUa.Driver.Cli.Common;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip.Cli.Commands;
+
+/// <summary>
+///     Read one Logix tag by symbolic path. Operator specifies <c>--tag</c> + <c>--type</c>;
+///     the CLI synthesises a one-tag driver config, reads once, prints the snapshot, shuts
+///     down. UDT / Structure reads are out of scope here — those need the member layout
+///     declared, which belongs in a real driver config.
+/// </summary>
+[Command("read", Description = "Read a single Logix tag by symbolic path.")]
+public sealed class ReadCommand : AbCipCommandBase
+{
+    [CommandOption("tag", 't', Description =
+        "Logix symbolic path. Controller scope: 'Motor01_Speed'. Program scope: " +
+        "'Program:Main.Motor01_Speed'. Array element: 'Recipe[3]'. UDT member: " +
+        "'Motor01.Speed'.", IsRequired = true)]
+    public string TagPath { get; init; } = default!;
+
+    [CommandOption("type", Description =
+        "Bool / SInt / Int / DInt / LInt / USInt / UInt / UDInt / ULInt / Real / LReal / " +
+        "String / Dt / Structure (default DInt).")]
+    public AbCipDataType DataType { get; init; } = AbCipDataType.DInt;
+
+    public override async ValueTask ExecuteAsync(IConsole console)
+    {
+        ConfigureLogging();
+        var ct = console.RegisterCancellationHandler();
+
+        var tagName = SynthesiseTagName(TagPath, DataType);
+        var tag = new AbCipTagDefinition(
+            Name: tagName,
+            DeviceHostAddress: Gateway,
+            TagPath: TagPath,
+            DataType: DataType,
+            Writable: false);
+        var options = BuildOptions([tag]);
+
+        await using var driver = new AbCipDriver(options, DriverInstanceId);
+        try
+        {
+            await driver.InitializeAsync("{}", ct);
+            var snapshot = await driver.ReadAsync([tagName], ct);
+            await console.Output.WriteLineAsync(SnapshotFormatter.Format(TagPath, snapshot[0]));
+        }
+        finally
+        {
+            await driver.ShutdownAsync(CancellationToken.None);
+        }
+    }
+
+    /// <summary>
+    ///     Tag-name key the driver uses internally. The path + type pair is already unique
+    ///     so we use them verbatim — keeps tag-level diagnostics readable without mangling.
+    /// </summary>
+    internal static string SynthesiseTagName(string tagPath, AbCipDataType type)
+        => $"{tagPath}:{type}";
+}