Refactor code structure for improved readability and maintainability; optimize performance in key functions.

src/Policy/StellaOps.Policy.Engine/Caching/IPolicyEvaluationCache.cs

@@ -1,4 +1,5 @@
 using System.Collections.Immutable;
+using StellaOps.Policy.Confidence.Models;
 using StellaOps.Policy.Engine.Evaluation;
 
 namespace StellaOps.Policy.Engine.Caching;
@@ -93,7 +94,8 @@ public sealed record PolicyEvaluationCacheEntry(
     string? ExceptionId,
     string CorrelationId,
     DateTimeOffset EvaluatedAt,
-    DateTimeOffset ExpiresAt);
+    DateTimeOffset ExpiresAt,
+    ConfidenceScore? Confidence);
 
 /// <summary>
 /// Result of a cache lookup.