convert: allow using quantized Mistral weight

[ngxson]

target model: https://huggingface.co/mistralai/Devstral-Small-2-24B-Instruct-2512

need --mistral-format, otherwise it has problem with tokenizer if you have problem with tokenizer conversion, install transformers version 5.0.0

[pwilkin]

Traceback (most recent call last):
  File "/devel/tools/llama.cpp/convert_hf_to_gguf.py", line 10635, in <module>
    main()
    ~~~~^^
  File "/devel/tools/llama.cpp/convert_hf_to_gguf.py", line 10629, in main
    model_instance.write()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/devel/tools/llama.cpp/convert_hf_to_gguf.py", line 660, in write
    self.prepare_tensors()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/devel/tools/llama.cpp/convert_hf_to_gguf.py", line 2540, in prepare_tensors
    super().prepare_tensors()
    ~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/devel/tools/llama.cpp/convert_hf_to_gguf.py", line 531, in prepare_tensors
    for new_name, data_torch in (self.modify_tensors(data_torch, name, bid)):
                                 ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
  File "/devel/tools/llama.cpp/convert_hf_to_gguf.py", line 2862, in modify_tensors
    assert data_torch.nelement() == 0 # unused by the model
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError

[ngxson]

should work now with --mistral-format

[bartowski1182]

confirming this works :)

https://huggingface.co/bartowski/mistralai_Devstral-Small-2-24B-Instruct-2512-GGUF

LGTM!