Function resolve_hf 

pub fn resolve_hf(
    repo_with_tag: &str,
    file: Option<&str>,
) -> Result<String, RuntimeError>

Resolve repo[:tag] to a local path, downloading if needed.

Pass file to select one file from a repo with several; leave it None to let llama.cpp pick.

This blocks and may download gigabytes. There is no progress callback on this entry point — llama.cpp prints progress through its own logger, so log controls what you see.

Errors

Returns RuntimeError::Failed if resolution or download fails, or RuntimeError::Nul for an interior NUL.