fix: address copilot comments

src/AnthropicClient/Models/Base64Source.cs

@@ -5,7 +5,7 @@ using AnthropicClient.Utils;
 namespace AnthropicClient.Models;
 
 /// <summary>
-/// Represents an base64 source.
+/// Represents a base64 source.
 /// </summary>
 public class Base64Source : Source
 {

src/AnthropicClient/Models/ContentBlockLocationCitation.cs

@@ -9,7 +9,7 @@ public class ContentBlockLocationCitation : Citation
 {
   /// <summary>
   /// Gets the start block index of the citation.
-  /// /// </summary>
+  /// </summary>
   [JsonPropertyName("start_block_index")]
   public int StartBlockIndex { get; init; }