docs: work on README

tests/AnthropicClient.Tests/Unit/Models/MessageDeltaEventDataTests.cs

@@ -18,7 +18,7 @@ public class MessageDeltaEventDataTests : SerializationTest
   public void Constructor_WhenCalled_ItShouldInitializeProperties()
   {
     var expectedDelta = new MessageDelta("max_tokens", "max_tokens");
-    var expectedUsage = new ChatUsage { InputTokens = 1, OutputTokens = 1 };
+    var expectedUsage = new Usage { InputTokens = 1, OutputTokens = 1 };
 
     var messageDeltaEventData = new MessageDeltaEventData(expectedDelta, expectedUsage);
 
@@ -30,7 +30,7 @@ public class MessageDeltaEventDataTests : SerializationTest
   public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
   {
     var expectedDelta = new MessageDelta("max_tokens", "max_tokens");
-    var expectedUsage = new ChatUsage { InputTokens = 1, OutputTokens = 1 };
+    var expectedUsage = new Usage { InputTokens = 1, OutputTokens = 1 };
 
     var messageDeltaEventData = new MessageDeltaEventData(expectedDelta, expectedUsage);
 
@@ -43,7 +43,7 @@ public class MessageDeltaEventDataTests : SerializationTest
   public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedValues()
   {
     var expectedDelta = new MessageDelta("max_tokens", "max_tokens");
-    var expectedUsage = new ChatUsage { InputTokens = 1, OutputTokens = 1 };
+    var expectedUsage = new Usage { InputTokens = 1, OutputTokens = 1 };
 
     var messageDeltaEventData = Deserialize<MessageDeltaEventData>(_testJson);