Auto: twincat-2.1 — ADS Sum-read / Sum-write

Closes #310

tests/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.IntegrationTests/TwinCATXarFixture.cs

@@ -134,3 +134,24 @@ public sealed class TwinCATTheoryAttribute : TheoryAttribute
                    "for setup; typical cause is the trial license expired or TWINCAT_TARGET_NETID is unset.";
     }
 }
+
+/// <summary>
+///     Perf-tier <c>[Fact]</c> equivalent. Runs only when the XAR runtime is reachable
+///     <em>and</em> <c>TWINCAT_PERF=1</c> is set. Perf tests are gated separately because
+///     they exercise the wire heavily (1000+ tags) + can extend test runs by tens of
+///     seconds — the operator opts in.
+/// </summary>
+public sealed class TwinCATPerfFactAttribute : FactAttribute
+{
+    public TwinCATPerfFactAttribute()
+    {
+        if (!TwinCATXarFixture.IsRuntimeAvailable())
+        {
+            Skip = "TwinCAT XAR not reachable. See docs/drivers/TwinCAT-Test-Fixture.md " +
+                   "for setup; typical cause is the trial license expired or TWINCAT_TARGET_NETID is unset.";
+            return;
+        }
+        if (Environment.GetEnvironmentVariable("TWINCAT_PERF") != "1")
+            Skip = "Perf tier disabled. Set TWINCAT_PERF=1 to run; see docs/drivers/TwinCAT-Test-Fixture.md §Performance.";
+    }
+}