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.AbLegacy.Cli/Commands/SubscribeCommand.cs

@@ -0,0 +1,78 @@
+using CliFx.Attributes;
+using CliFx.Infrastructure;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.Cli.Common;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Cli.Commands;
+
+/// <summary>
+///     Watch a PCCC file address via polled subscription until Ctrl+C. Mirrors the Modbus /
+///     AB CIP subscribe shape — PollGroupEngine handles the tick loop.
+/// </summary>
+[Command("subscribe", Description = "Watch a PCCC file address via polled subscription until Ctrl+C.")]
+public sealed class SubscribeCommand : AbLegacyCommandBase
+{
+    [CommandOption("address", 'a', Description = "PCCC file address — same format as `read`.", IsRequired = true)]
+    public string Address { get; init; } = default!;
+
+    [CommandOption("type", 't', Description =
+        "Bit / Int / Long / Float / AnalogInt / String / TimerElement / CounterElement / " +
+        "ControlElement (default Int).")]
+    public AbLegacyDataType DataType { get; init; } = AbLegacyDataType.Int;
+
+    [CommandOption("interval-ms", 'i', Description =
+        "Publishing interval in milliseconds (default 1000).")]
+    public int IntervalMs { get; init; } = 1000;
+
+    public override async ValueTask ExecuteAsync(IConsole console)
+    {
+        ConfigureLogging();
+        var ct = console.RegisterCancellationHandler();
+
+        var tagName = ReadCommand.SynthesiseTagName(Address, DataType);
+        var tag = new AbLegacyTagDefinition(
+            Name: tagName,
+            DeviceHostAddress: Gateway,
+            Address: Address,
+            DataType: DataType,
+            Writable: false);
+        var options = BuildOptions([tag]);
+
+        await using var driver = new AbLegacyDriver(options, DriverInstanceId);
+        ISubscriptionHandle? handle = null;
+        try
+        {
+            await driver.InitializeAsync("{}", ct);
+
+            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);
+            };
+
+            handle = await driver.SubscribeAsync([tagName], TimeSpan.FromMilliseconds(IntervalMs), ct);
+
+            await console.Output.WriteLineAsync(
+                $"Subscribed to {Address} @ {IntervalMs}ms. Ctrl+C to stop.");
+            try
+            {
+                await Task.Delay(System.Threading.Timeout.InfiniteTimeSpan, ct);
+            }
+            catch (OperationCanceledException)
+            {
+                // Expected on Ctrl+C.
+            }
+        }
+        finally
+        {
+            if (handle is not null)
+            {
+                try { await driver.UnsubscribeAsync(handle, CancellationToken.None); }
+                catch { /* teardown best-effort */ }
+            }
+            await driver.ShutdownAsync(CancellationToken.None);
+        }
+    }
+}