convert : add Devstral-2 (Ministral3ForCausalLM) arch (#18972)

* Add Ministral3ForCausalLM architeture

This adds support for newer architectres like Devstral-2

* removed blank line found after function decorator

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

---------

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

convert_hf_to_gguf.py

@@ -2979,7 +2979,10 @@ class Llama4VisionModel(MmprojModel):
         return []
 
 
-@ModelBase.register("Mistral3ForConditionalGeneration")
+@ModelBase.register(
+    "Mistral3ForConditionalGeneration",
+    "Ministral3ForCausalLM",
+)
 class Mistral3Model(LlamaModel):
     model_arch = gguf.MODEL_ARCH.MISTRAL3