feat(app): better error message for failed model probe

- Old: No valid config found
- New: Unable to determine model type

Author: psychedelicious

invokeai/backend/model_manager/config.py

@@ -187,7 +187,7 @@ def classify(mod: str | Path | ModelOnDisk, hash_algo: HASHING_ALGORITHMS = "bla
             else:
                 return config_cls.from_model_on_disk(mod, **overrides)
 
-        raise InvalidModelConfigException("No valid config found")
+        raise InvalidModelConfigException("Unable to determine model type")
 
     @classmethod
     def get_tag(cls) -> Tag: