probes: fileformats probe fails when targeting a local modal path

[jmartin-tech]

The fileformats are limited to huggingface generators, however there are cases where the generator can load a local checkpoint that would not be complatible with this probe. This is due the the expectation that the model under test is published for file enumeration via the huggingface_hub utility library.

Contrived example:

python -m garak -m huffingface.Model -n /usr/local/checkpoints/Mistral-NeMo-Minitron-8B-Instruct -p fileformats

Current trace reported in logs:

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/garak/cli.py", line 530, in main
    command.probewise_run(
  File "/usr/local/lib/python3.10/site-packages/garak/command.py", line 237, in probewise_run
    probewise_h.run(generator, probe_names, evaluator, buffs)
  File "/usr/local/lib/python3.10/site-packages/garak/harnesses/probewise.py", line 107, in run
    h.run(model, [probe], detectors, evaluator, announce_probe=False)
  File "/usr/local/lib/python3.10/site-packages/garak/harnesses/base.py", line 114, in run
    attempt_results = probe.probe(model)
  File "/usr/local/lib/python3.10/site-packages/garak/probes/fileformats.py", line 63, in probe
    repo_filenames = huggingface_hub.list_repo_files(generator.name)
  File "/usr/local/lib/python3.10/site-packages/huggingface_hub/utils/_validators.py", line 106, in _inner_fn
    validate_repo_id(arg_value)
  File "/usr/local/lib/python3.10/site-packages/huggingface_hub/utils/_validators.py", line 154, in validate_repo_id
    raise HFValidationError(
huggingface_hub.errors.HFValidationError: Repo id must be in the form 'repo_name' or 'namespace/repo_name': '/usr/local/checkpoints/Mistral-NeMo-Minitron-8B-Instruct/'. Use `repo_type` argument if needed.

This probe needs to be able to either skip for local model paths or follow an alternative file gathering approach.