Add cross-platform OPC UA client stack: shared library, CLI tool, and Avalonia UI

Implements Client.Shared (IOpcUaClientService with connection lifecycle, failover,
browse, read/write, subscriptions, alarms, history, redundancy), Client.CLI (8 CliFx
commands mirroring tools/opcuacli-dotnet), and Client.UI (Avalonia desktop app with
tree browser, read/write, subscriptions, alarms, and history tabs). All three target
.NET 10 and are covered by 249 unit tests.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/ZB.MOM.WW.LmxOpcUa.Client.Shared.Tests/Fakes/FakeSubscriptionAdapter.cs

@@ -0,0 +1,88 @@
+using Opc.Ua;
+using ZB.MOM.WW.LmxOpcUa.Client.Shared.Adapters;
+
+namespace ZB.MOM.WW.LmxOpcUa.Client.Shared.Tests.Fakes;
+
+internal sealed class FakeSubscriptionAdapter : ISubscriptionAdapter
+{
+    private uint _nextHandle = 100;
+    private readonly Dictionary<uint, (NodeId NodeId, Action<string, DataValue>? DataCallback, Action<EventFieldList>? EventCallback)> _items = new();
+
+    public uint SubscriptionId { get; set; } = 42;
+    public bool Deleted { get; private set; }
+    public bool ConditionRefreshCalled { get; private set; }
+    public bool ThrowOnConditionRefresh { get; set; }
+    public int AddDataChangeCount { get; private set; }
+    public int AddEventCount { get; private set; }
+    public int RemoveCount { get; private set; }
+
+    public Task<uint> AddDataChangeMonitoredItemAsync(NodeId nodeId, int samplingIntervalMs, Action<string, DataValue> onDataChange, CancellationToken ct)
+    {
+        AddDataChangeCount++;
+        var handle = _nextHandle++;
+        _items[handle] = (nodeId, onDataChange, null);
+        return Task.FromResult(handle);
+    }
+
+    public Task RemoveMonitoredItemAsync(uint clientHandle, CancellationToken ct)
+    {
+        RemoveCount++;
+        _items.Remove(clientHandle);
+        return Task.CompletedTask;
+    }
+
+    public Task<uint> AddEventMonitoredItemAsync(NodeId nodeId, int samplingIntervalMs, EventFilter filter, Action<EventFieldList> onEvent, CancellationToken ct)
+    {
+        AddEventCount++;
+        var handle = _nextHandle++;
+        _items[handle] = (nodeId, null, onEvent);
+        return Task.FromResult(handle);
+    }
+
+    public Task ConditionRefreshAsync(CancellationToken ct)
+    {
+        ConditionRefreshCalled = true;
+        if (ThrowOnConditionRefresh)
+            throw new InvalidOperationException("Condition refresh not supported");
+        return Task.CompletedTask;
+    }
+
+    public Task DeleteAsync(CancellationToken ct)
+    {
+        Deleted = true;
+        _items.Clear();
+        return Task.CompletedTask;
+    }
+
+    public void Dispose()
+    {
+        _items.Clear();
+    }
+
+    /// <summary>
+    /// Simulates a data change notification for testing.
+    /// </summary>
+    public void SimulateDataChange(uint handle, DataValue value)
+    {
+        if (_items.TryGetValue(handle, out var item) && item.DataCallback != null)
+        {
+            item.DataCallback(item.NodeId.ToString(), value);
+        }
+    }
+
+    /// <summary>
+    /// Simulates an event notification for testing.
+    /// </summary>
+    public void SimulateEvent(uint handle, EventFieldList eventFields)
+    {
+        if (_items.TryGetValue(handle, out var item) && item.EventCallback != null)
+        {
+            item.EventCallback(eventFields);
+        }
+    }
+
+    /// <summary>
+    /// Gets the handles of all active items.
+    /// </summary>
+    public IReadOnlyCollection<uint> ActiveHandles => _items.Keys.ToList();
+}