Fix audit findings for coverage, architecture checks, and XML docs

tests/CBDD.Tests/CompressionCompatibilityTests.cs

@@ -9,6 +9,9 @@ namespace ZB.MOM.WW.CBDD.Tests;
 
 public class CompressionCompatibilityTests
 {
+    /// <summary>
+    /// Verifies opening legacy uncompressed files with compression enabled does not mutate database bytes.
+    /// </summary>
     [Fact]
     public void OpeningLegacyUncompressedFile_WithCompressionEnabled_ShouldNotMutateDbFile()
     {
@@ -56,6 +59,9 @@ public class CompressionCompatibilityTests
         }
     }
 
+    /// <summary>
+    /// Verifies mixed compressed and uncompressed documents remain readable after partial migration.
+    /// </summary>
     [Fact]
     public void MixedFormatDocuments_ShouldRemainReadableAfterPartialMigration()
     {