Function build_repositories_modal_fields 

pub fn build_repositories_modal_fields(
    repos_path: Option<&Path>,
    pacman_conf_path: &Path,
) -> (Vec<RepositoryModalRow>, Option<String>, Vec<String>)

What: Merge repos.conf, pacman scan, and optional keyring snapshot into modal rows.

Inputs:

• repos_path: Resolved repos.conf path, if any.
• pacman_conf_path: Usually /etc/pacman.conf.

Output:

• (rows, repos_conf_error, pacman_warnings) for the Repositories modal UI.

Details:

• When repos_path is None, rows stay empty (user has no config file yet).
• Uses one batched pacman-key --list-keys when possible for fingerprint checks.