Change kattgpt tokenizer model to gpt-5

Author: selfdocumentingcode

src/Kattbot/NotificationHandlers/KattGptMessageHandler.cs

@@ -24,10 +24,9 @@ public class KattGptMessageHandler : BaseNotificationHandler,
     INotificationHandler<MessageCreatedNotification>
 {
     private const string ChatGptModel = "gpt-5";
-    private const string TokenizerModel = "gpt-4o"; // TODO update to gpt5 when available
+    private const string TokenizerModel = "gpt-5";
     private const string DefaultReasoningEffort = "minimal";
 
-    private const float DefaultTemperature = 1.1f;
     private const int MaxTotalTokens = 24_576;
     private const int MaxTokensToGenerate = 960; // Roughly the limit of 2 Discord messages
     private const string MessageSplitToken = "[cont.] ";