[export] handle NotImplementedError in export_model for transformers>=5.0 (fixes #10410) (#10438)

Co-authored-by: octo-patch <octo-patch@github.com>

src/llamafactory/train/tuner.py

@@ -180,7 +180,15 @@ def export_model(args: Optional[dict[str, Any]] = None) -> None:
     if not is_transformers_version_greater_than("5.0.0"):
         save_kwargs["safe_serialization"] = not model_args.export_legacy_format
 
+    try:
         model.save_pretrained(**save_kwargs)
+    except NotImplementedError as err:
+        raise RuntimeError(
+            "Failed to export model: weight conversion reversal is not supported for this model architecture "
+            "(NotImplementedError in transformers.core_model_loading.reverse_op). "
+            "This is a known issue with transformers>=5.0 for certain model types (e.g. Mistral/Ministral). "
+            "Workarounds: (1) use transformers<5.0, or (2) report the issue to the transformers repository."
+        ) from err
 
     if model_args.export_hub_model_id is not None:
         # Prepare push arguments (safe_serialization removed in transformers v5.0.0)