Function release_download_url 

pub fn release_download_url(
    repo: &str,
    release_tag: &str,
    version: &str,
    arch: BoxArch,
) -> String

GitHub Release download URL for a box tar.gz asset.

release_tag is the GitHub tag (v0.1.0 or tip Pre-release dev-preview). The asset filename still embeds version (Cargo workspace version).