Function raw_manifest_url 

pub fn raw_manifest_url(
    owner: &str,
    repository: &str,
    commit_sha: Option<&str>,
) -> String

Convention: the raw-GitHub URL we’d fetch objectiveai.json from for a given (owner, repository, optional commit sha). Defaults to HEAD when no commit is supplied. Lifted out so the cli and the SDK’s own install_plugin wrapper share one source of truth.