TwinCAT follow-up — Symbol browser via AdsClient + SymbolLoaderFactory. Closes task #188. Adds ITwinCATClient.BrowseSymbolsAsync — IAsyncEnumerable yielding TwinCATDiscoveredSymbol (InstancePath + mapped TwinCATDataType + ReadOnly flag) from the target's flat symbol table. AdsTwinCATClient implementation uses SymbolLoaderFactory.Create(_client, new SymbolLoaderSettings(SymbolsLoadMode.Flat)) + iterates loader.Symbols, maps IEC 61131-3 type names (BOOL/SINT/INT/DINT/LINT/REAL/LREAL/STRING/WSTRING/TIME/DATE/DT/TOD + BYTE/WORD/DWORD/LWORD unsigned-word aliases) through MapSymbolTypeName, checks SymbolAccessRights.Write bit for writable vs read-only. Unsupported types (UDTs / function blocks / arrays / pointers) surface with DataType=null so callers can skip or recurse. TwinCATDriverOptions.EnableControllerBrowse — new bool, default false to preserve the strict-config path. When true, DiscoverAsync iterates each device's BrowseSymbolsAsync, filters via TwinCATSystemSymbolFilter (rejects TwinCAT_*, Constants.*, Mc_*, __*, Global_Version* prefixes + anything empty), skips null-DataType symbols, emits surviving symbols under a per-device Discovered/ sub-folder with InstancePath as both FullName + BrowseName + ReadOnly→ViewOnly/writable→Operate. Pre-declared tags from TwinCATDriverOptions.Tags always emit regardless. Browse failure is non-fatal — exception caught + swallowed, pre-declared tags stay in the address space, operators see the failure in driver health on next read. TwinCATSystemSymbolFilter static class mirrors AbCipSystemTagFilter's shape with TwinCAT-specific prefixes. Fake client updated — BrowseResults list for test setup + FireNotification-style single-invocation on each subscribe, ThrowOnBrowse flag for failure testing. 8 new unit tests — strict path emits only pre-declared when EnableControllerBrowse=false, browse enabled adds Discovered/ folder, filter rejects system prefixes, null-DataType symbols skipped, ReadOnly symbols surface ViewOnly, browse failure leaves pre-declared intact, SystemSymbolFilter theory (10 cases). Total TwinCAT unit tests now 110/110 passing (+17 from the native-notification merge's 93); full solution builds 0 errors; other drivers untouched.

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

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

@@ -1,3 +1,4 @@
+using System.Runtime.CompilerServices;
 using ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;
 
 namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests;
@@ -82,6 +83,23 @@ internal class FakeTwinCATClient : ITwinCATClient
                 n.OnChange(symbolPath, value);
     }
 
+    // ---- symbol browser fake ----
+
+    public List<TwinCATDiscoveredSymbol> BrowseResults { get; } = new();
+    public bool ThrowOnBrowse { get; set; }
+
+    public virtual async IAsyncEnumerable<TwinCATDiscoveredSymbol> BrowseSymbolsAsync(
+        [EnumeratorCancellation] CancellationToken cancellationToken)
+    {
+        if (ThrowOnBrowse) throw Exception ?? new InvalidOperationException("fake browse failure");
+        await Task.CompletedTask;
+        foreach (var sym in BrowseResults)
+        {
+            if (cancellationToken.IsCancellationRequested) yield break;
+            yield return sym;
+        }
+    }
+
     public sealed class FakeNotification(
         string symbolPath, TwinCATDataType type, int? bitIndex,
         Action<string, object?> onChange, FakeTwinCATClient owner) : ITwinCATNotificationHandle