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

tests/CBDD.Tests/SchemaPersistenceTests.cs

@@ -17,18 +17,27 @@ public class SchemaPersistenceTests : IDisposable
     private readonly string _dbPath;
     private readonly Shared.TestDbContext _db;
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SchemaPersistenceTests"/> class.
+    /// </summary>
     public SchemaPersistenceTests()
     {
         _dbPath = Path.Combine(Path.GetTempPath(), $"schema_test_{Guid.NewGuid()}.db");
         _db = new Shared.TestDbContext(_dbPath);
     }
 
+    /// <summary>
+    /// Disposes test resources and removes temporary files.
+    /// </summary>
     public void Dispose()
     {
         _db.Dispose();
         if (File.Exists(_dbPath)) File.Delete(_dbPath);
     }
 
+    /// <summary>
+    /// Verifies BSON schema serialization and deserialization round-trips correctly.
+    /// </summary>
     [Fact]
     public void BsonSchema_Serialization_RoundTrip()
     {
@@ -81,6 +90,9 @@ public class SchemaPersistenceTests : IDisposable
         schema.Equals(roundTrip).ShouldBeTrue();
     }
 
+    /// <summary>
+    /// Verifies collection metadata is persisted and reloaded correctly.
+    /// </summary>
     [Fact]
     public void StorageEngine_Collections_Metadata_Persistence()
     {
@@ -103,6 +115,9 @@ public class SchemaPersistenceTests : IDisposable
         loaded.Indexes[0].Name.ShouldBe("age");
     }
 
+    /// <summary>
+    /// Verifies schema versioning appends new schema versions correctly.
+    /// </summary>
     [Fact]
     public void StorageEngine_Schema_Versioning()
     {
@@ -125,6 +140,9 @@ public class SchemaPersistenceTests : IDisposable
         schemas[1].Title.ShouldBe("V2");
     }
 
+    /// <summary>
+    /// Verifies collection startup integrates schema versioning behavior.
+    /// </summary>
     [Fact]
     public void DocumentCollection_Integrates_Schema_Versioning_On_Startup()
     {
@@ -186,6 +204,9 @@ public class SchemaPersistenceTests : IDisposable
         }
     }
 
+    /// <summary>
+    /// Verifies persisted documents include the schema version field.
+    /// </summary>
     [Fact]
     public void Document_Contains_Schema_Version_Field()
     {