Auto: twincat-4.1 — nested UDT browse via online type walker

Closes #315

tests/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests/FakeTwinCATClient.cs

@@ -361,9 +361,18 @@ internal class FakeTwinCATClient : ITwinCATClient
     public List<TwinCATDiscoveredSymbol> BrowseResults { get; } = new();
     public bool ThrowOnBrowse { get; set; }
 
+    /// <summary>
+    ///     PR 4.1 / #315 — captures the most recent <c>maxArrayExpansion</c> the driver passed
+    ///     so tests can assert the option threaded through. Defaults to <c>-1</c> until the
+    ///     first browse call; <c>0</c> would be a meaningful (degenerate) caller value.
+    /// </summary>
+    public int LastBrowseMaxArrayExpansion { get; private set; } = -1;
+
     public virtual async IAsyncEnumerable<TwinCATDiscoveredSymbol> BrowseSymbolsAsync(
+        int maxArrayExpansion,
         [EnumeratorCancellation] CancellationToken cancellationToken)
     {
+        LastBrowseMaxArrayExpansion = maxArrayExpansion;
         if (ThrowOnBrowse) throw Exception ?? new InvalidOperationException("fake browse failure");
         await Task.CompletedTask;
         foreach (var sym in BrowseResults)