fix: Chatterbox uses separate classes per variant, remove turbo

ChatterboxTTS and ChatterboxMultilingualTTS are separate classes.
Turbo variant doesn't exist in chatterbox-tts 0.1.7.
Multilingual generate() requires language_id parameter.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

kischdle/llmux/tests/test_model_registry.py

@@ -10,7 +10,7 @@ def registry():
 
 def test_list_virtual_models(registry):
     models = registry.list_virtual_models()
-    assert len(models) == 16
+    assert len(models) == 15
     names = [m["id"] for m in models]
     assert "Qwen3.5-9B-FP8-Thinking" in names
     assert "GPT-OSS-20B-High" in names