fix: update MiniMax model names to M2.5/M2.1

Fixes #294 - Updates MiniMax model names from the old ABAB 6.5 series to
the current M2.5/M2.1 series.

- Updated wizard model selection for MiniMax provider
- Fixed DiscordConfig test cases to include new listen_to_bots field

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/onboard/wizard.rs

@@ -799,8 +799,9 @@ fn setup_provider() -> Result<(String, String, String)> {
             ("glm-4-flash", "GLM-4 Flash (fast)"),
         ],
         "minimax" => vec![
-            ("abab6.5s-chat", "ABAB 6.5s Chat"),
-            ("abab6.5-chat", "ABAB 6.5 Chat"),
+            ("MiniMax-M2.5", "MiniMax M2.5 (latest flagship)"),
+            ("MiniMax-M2.5-highspeed", "MiniMax M2.5 Highspeed (faster)"),
+            ("MiniMax-M2.1", "MiniMax M2.1 (previous gen)"),
         ],
         "ollama" => vec![
             ("llama3.2", "Llama 3.2 (recommended local)"),