Task #253 — E2E CLI test scripts + FOCAS test-client CLI

The driver-layer integration tests confirm the driver sees the PLC, and
the Client.CLI tests confirm the client sees the server. Nothing glued
them end-to-end until this PR.

- scripts/e2e/_common.ps1: shared helpers — CLI invocation (published-
  binary OR `dotnet run` fallback), Test-Probe / Test-DriverLoopback /
  Test-ServerBridge (all return @{Passed;Reason} hashtables).
- scripts/e2e/test-<modbus|abcip|ablegacy|s7|focas|twincat>.ps1: per-
  driver three-stage script (probe → driver-loopback → server-bridge).
  AB Legacy / FOCAS / TwinCAT are gated behind *_TRUST_WIRE env vars
  since they need real hardware (#222) or a licensed runtime (#221).
- scripts/e2e/test-phase7-virtualtags.ps1: writes a Modbus HR, reads
  the server-side VirtualTag (VT = input * 2) back via OPC UA, triggers
  + clears a scripted alarm. Exercises the Phase 7 CachedTagUpstreamSource
  + ScriptedAlarmEngine path.
- scripts/e2e/test-all.ps1: reads e2e-config.json sidecar, runs each
  present driver, prints a FINAL MATRIX (PASS/FAIL/SKIP). Missing
  sections SKIP rather than fail hard.
- scripts/e2e/e2e-config.sample.json: commented sample — each dev's
  NodeIds are local-seed-specific so e2e-config.json is .gitignore-d.
- scripts/e2e/README.md: full walkthrough — prereqs, three-stage design,
  env-var gates, expected matrix, why this is separate from `dotnet test`.

Tasks #249-#251 shipped Modbus/AbCip/AbLegacy/S7/TwinCAT CLIs but left
FOCAS out. Since test-focas.ps1 needs it, the 6th CLI ships here:

- src/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Cli: probe/read/write/subscribe
  commands, AssemblyName `otopcua-focas-cli`. WriteCommand.ParseValue
  handles the full FocasDataType enum (Bit/Byte/Int16/Int32/Float32/
  Float64/String — no UInt variants; the FOCAS protocol exposes signed
  PMC + Fanuc-Float only). Default DataType is Int16 to match the PMC
  register convention.

Full-solution build clean (0 errors). FOCAS CLI wired into
ZB.MOM.WW.OtOpcUa.slnx. No .Tests project for the FOCAS CLI yet —
symmetric with how ProbeCommand has no unit-testable pure logic in the
other 5 CLIs either; WriteCommand.ParseValue parity will land in a
follow-up to keep this PR scoped.

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

src/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Cli/Commands/SubscribeCommand.cs

@@ -0,0 +1,76 @@
+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.FOCAS.Cli.Commands;
+
+/// <summary>
+///     Watch a FOCAS address via polled subscription until Ctrl+C. FOCAS has no push
+///     model; <c>PollGroupEngine</c> handles the tick loop.
+/// </summary>
+[Command("subscribe", Description = "Watch a FOCAS address via polled subscription until Ctrl+C.")]
+public sealed class SubscribeCommand : FocasCommandBase
+{
+    [CommandOption("address", 'a', Description = "FOCAS address — same format as `read`.", IsRequired = true)]
+    public string Address { get; init; } = default!;
+
+    [CommandOption("type", 't', Description =
+        "Bit / Byte / Int16 / Int32 / Float32 / Float64 / String (default Int16).")]
+    public FocasDataType DataType { get; init; } = FocasDataType.Int16;
+
+    [CommandOption("interval-ms", 'i', Description = "Publishing interval ms (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 FocasTagDefinition(
+            Name: tagName,
+            DeviceHostAddress: HostAddress,
+            Address: Address,
+            DataType: DataType,
+            Writable: false);
+        var options = BuildOptions([tag]);
+
+        await using var driver = new FocasDriver(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);
+        }
+    }
+}