stabilizaiton work - projects rework for maintenanceability and ui livening

src/__Libraries/__Tests/StellaOps.TestKit.Tests/ObservabilityContractTests.MetricsContractAssert.cs

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+using System.Collections.Generic;
+using System.Diagnostics.Metrics;
+using FluentAssertions;
+using StellaOps.TestKit.Observability;
+using Xunit;
+
+namespace StellaOps.TestKit.Tests;
+
+public sealed partial class ObservabilityContractTests
+{
+    [Fact]
+    public void MetricExists_Present_NoException()
+    {
+        using var meter = new Meter("TestMeter1");
+        using var capture = new MetricsCapture("TestMeter1");
+
+        var counter = meter.CreateCounter<long>("test_requests_total");
+        counter.Add(1);
+
+        var act = () => MetricsContractAssert.MetricExists(capture, "test_requests_total");
+
+        act.Should().NotThrow();
+    }
+
+    [Fact]
+    public void MetricExists_Missing_ThrowsContractViolation()
+    {
+        using var meter = new Meter("TestMeter2");
+        using var capture = new MetricsCapture("TestMeter2");
+
+        var counter = meter.CreateCounter<long>("some_other_metric");
+        counter.Add(1);
+
+        var act = () => MetricsContractAssert.MetricExists(capture, "missing_metric");
+
+        act.Should().Throw<ContractViolationException>()
+            .WithMessage("*missing_metric*not found*");
+    }
+
+    [Fact]
+    public void LabelCardinalityBounded_WithinThreshold_NoException()
+    {
+        using var meter = new Meter("TestMeter3");
+        using var capture = new MetricsCapture("TestMeter3");
+
+        var counter = meter.CreateCounter<long>("http_requests_total");
+        counter.Add(1, new KeyValuePair<string, object?>("method", "GET"));
+        counter.Add(1, new KeyValuePair<string, object?>("method", "POST"));
+
+        var act = () => MetricsContractAssert.LabelCardinalityBounded(
+            capture,
+            "http_requests_total",
+            maxLabels: 10);
+
+        act.Should().NotThrow();
+    }
+
+    [Fact]
+    public void LabelCardinalityBounded_ExceedsThreshold_ThrowsContractViolation()
+    {
+        using var meter = new Meter("TestMeter4");
+        using var capture = new MetricsCapture("TestMeter4");
+
+        var counter = meter.CreateCounter<long>("requests_by_user");
+
+        for (int i = 0; i < 10; i++)
+        {
+            counter.Add(1, new KeyValuePair<string, object?>("user_id", $"user-{i}"));
+        }
+
+        var act = () => MetricsContractAssert.LabelCardinalityBounded(
+            capture,
+            "requests_by_user",
+            maxLabels: 5);
+
+        act.Should().Throw<ContractViolationException>()
+            .WithMessage("*cardinality*exceeds*");
+    }
+}