test: finish diagnostic classification

tests/AcDream.Core.Tests/Physics/CellarUpTrajectoryReplayTests.cs

@@ -737,6 +737,7 @@ public class CellarUpTrajectoryReplayTests : IDisposable
     /// Always passes; this is a one-shot tool, not a regression.
     /// </summary>
     [Fact]
+    [Trait("Purpose", "Diagnostic")]
     public void LiveCompare_FirstCap_DiagnosticDump()
     {
         PhysicsDiagnostics.ProbeResolveEnabled    = true;