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

tests/CBDD.Tests/BsonDocumentAndBufferWriterTests.cs

@@ -8,6 +8,9 @@ namespace ZB.MOM.WW.CBDD.Tests;
 
 public class BsonDocumentAndBufferWriterTests
 {
+    /// <summary>
+    /// Verifies BSON document creation and typed retrieval roundtrip.
+    /// </summary>
     [Fact]
     public void BsonDocument_Create_And_TryGet_RoundTrip()
     {
@@ -42,6 +45,9 @@ public class BsonDocumentAndBufferWriterTests
         reader.ReadDocumentSize().ShouldBeGreaterThan(0);
     }
 
+    /// <summary>
+    /// Verifies typed getters return false for missing fields and type mismatches.
+    /// </summary>
     [Fact]
     public void BsonDocument_TryGet_Should_Return_False_For_Missing_Or_Wrong_Type()
     {
@@ -64,6 +70,9 @@ public class BsonDocumentAndBufferWriterTests
         wrapped.TryGetObjectId("age", out _).ShouldBeFalse();
     }
 
+    /// <summary>
+    /// Verifies the BSON document builder grows its internal buffer for large documents.
+    /// </summary>
     [Fact]
     public void BsonDocumentBuilder_Should_Grow_Buffer_When_Document_Is_Large()
     {
@@ -90,6 +99,9 @@ public class BsonDocumentAndBufferWriterTests
         value.ShouldBe(180);
     }
 
+    /// <summary>
+    /// Verifies BSON buffer writer emits expected nested document and array layout.
+    /// </summary>
     [Fact]
     public void BsonBufferWriter_Should_Write_Nested_Document_And_Array()
     {
@@ -151,6 +163,9 @@ public class BsonDocumentAndBufferWriterTests
         reader.ReadBsonType().ShouldBe(BsonType.EndOfDocument);
     }
 
+    /// <summary>
+    /// Verifies single-byte and C-string span reads operate correctly.
+    /// </summary>
     [Fact]
     public void BsonSpanReader_ReadByte_And_ReadCStringSpan_Should_Work()
     {