Refactor code structure and optimize performance across multiple modules

src/Policy/__Tests/StellaOps.Policy.Tests/PolicyValidationCliTests.cs

@@ -8,7 +8,8 @@ namespace StellaOps.Policy.Tests;
 
 public class PolicyValidationCliTests
 {
-    [Fact]
+    [Trait("Category", TestCategories.Unit)]
+        [Fact]
     public async Task RunAsync_EmitsCanonicalDigest_OnValidPolicy()
     {
         var tmp = Path.GetTempFileName();
@@ -41,6 +42,7 @@ public class PolicyValidationCliTests
 
             using var output = new StringWriter();
             using var error = new StringWriter();
+using StellaOps.TestKit;
             var cli = new PolicyValidationCli(output, error);
 
             var exit = await cli.RunAsync(options);