feat(lmxproxy): phase 1 — v2 protocol types and domain model

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

lmxproxy/tests/ZB.MOM.WW.LmxProxy.Client.Tests/Domain/VtqTests.cs

@@ -0,0 +1,33 @@
+using FluentAssertions;
+using Xunit;
+using ZB.MOM.WW.LmxProxy.Client.Domain;
+
+namespace ZB.MOM.WW.LmxProxy.Client.Tests.Domain;
+
+public class VtqTests
+{
+    [Fact]
+    public void Good_FactoryMethod()
+    {
+        var vtq = Vtq.Good(42.0);
+        vtq.Value.Should().Be(42.0);
+        vtq.Quality.Should().Be(Quality.Good);
+        vtq.Timestamp.Kind.Should().Be(DateTimeKind.Utc);
+    }
+
+    [Fact]
+    public void Bad_FactoryMethod()
+    {
+        var vtq = Vtq.Bad();
+        vtq.Value.Should().BeNull();
+        vtq.Quality.Should().Be(Quality.Bad);
+    }
+
+    [Fact]
+    public void Uncertain_FactoryMethod()
+    {
+        var vtq = Vtq.Uncertain("stale");
+        vtq.Value.Should().Be("stale");
+        vtq.Quality.Should().Be(Quality.Uncertain);
+    }
+}