Implement LmxOpcUa server — all 6 phases complete

Full OPC UA server on .NET Framework 4.8 (x86) exposing AVEVA System
Platform Galaxy tags via MXAccess. Mirrors Galaxy object hierarchy as
OPC UA address space, translating contained-name browse paths to
tag-name runtime references.

Components implemented:
- Configuration: AppConfiguration with 4 sections, validator
- Domain: ConnectionState, Quality, Vtq, MxDataTypeMapper, error codes
- MxAccess: StaComThread, MxAccessClient (partial classes), MxProxyAdapter
  using strongly-typed ArchestrA.MxAccess COM interop
- Galaxy Repository: SQL queries (hierarchy, attributes, change detection),
  ChangeDetectionService with auto-rebuild on deploy
- OPC UA Server: LmxNodeManager (CustomNodeManager2), LmxOpcUaServer,
  OpcUaServerHost with programmatic config, SecurityPolicy None
- Status Dashboard: HTTP server with HTML/JSON/health endpoints
- Integration: Full 14-step startup, graceful shutdown, component wiring

175 tests (174 unit + 1 integration), all passing.

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

tests/ZB.MOM.WW.LmxOpcUa.Tests/Status/HealthCheckServiceTests.cs

@@ -0,0 +1,82 @@
+using System;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.LmxOpcUa.Host.Domain;
+using ZB.MOM.WW.LmxOpcUa.Host.Metrics;
+using ZB.MOM.WW.LmxOpcUa.Host.Status;
+
+namespace ZB.MOM.WW.LmxOpcUa.Tests.Status
+{
+    public class HealthCheckServiceTests
+    {
+        private readonly HealthCheckService _sut = new();
+
+        [Fact]
+        public void NotConnected_ReturnsUnhealthy()
+        {
+            var result = _sut.CheckHealth(ConnectionState.Disconnected, null);
+            result.Status.ShouldBe("Unhealthy");
+            result.Color.ShouldBe("red");
+            result.Message.ShouldContain("not connected");
+        }
+
+        [Fact]
+        public void Connected_NoMetrics_ReturnsHealthy()
+        {
+            var result = _sut.CheckHealth(ConnectionState.Connected, null);
+            result.Status.ShouldBe("Healthy");
+            result.Color.ShouldBe("green");
+        }
+
+        [Fact]
+        public void Connected_GoodMetrics_ReturnsHealthy()
+        {
+            using var metrics = new PerformanceMetrics();
+            for (int i = 0; i < 200; i++)
+                metrics.RecordOperation("Read", TimeSpan.FromMilliseconds(10), true);
+
+            var result = _sut.CheckHealth(ConnectionState.Connected, metrics);
+            result.Status.ShouldBe("Healthy");
+        }
+
+        [Fact]
+        public void Connected_LowSuccessRate_ReturnsDegraded()
+        {
+            using var metrics = new PerformanceMetrics();
+            for (int i = 0; i < 40; i++)
+                metrics.RecordOperation("Read", TimeSpan.FromMilliseconds(10), true);
+            for (int i = 0; i < 80; i++)
+                metrics.RecordOperation("Read", TimeSpan.FromMilliseconds(10), false);
+
+            var result = _sut.CheckHealth(ConnectionState.Connected, metrics);
+            result.Status.ShouldBe("Degraded");
+            result.Color.ShouldBe("yellow");
+        }
+
+        [Fact]
+        public void IsHealthy_Connected_ReturnsTrue()
+        {
+            _sut.IsHealthy(ConnectionState.Connected, null).ShouldBe(true);
+        }
+
+        [Fact]
+        public void IsHealthy_Disconnected_ReturnsFalse()
+        {
+            _sut.IsHealthy(ConnectionState.Disconnected, null).ShouldBe(false);
+        }
+
+        [Fact]
+        public void Error_ReturnsUnhealthy()
+        {
+            var result = _sut.CheckHealth(ConnectionState.Error, null);
+            result.Status.ShouldBe("Unhealthy");
+        }
+
+        [Fact]
+        public void Reconnecting_ReturnsUnhealthy()
+        {
+            var result = _sut.CheckHealth(ConnectionState.Reconnecting, null);
+            result.Status.ShouldBe("Unhealthy");
+        }
+    }
+}