Function compute_and_ensure_account_dir 

pub(crate) fn compute_and_ensure_account_dir(
    store: &Store,
    existing_account_id: &str,
    provider_id: &str,
    auth_env: &mut HashMap<String, String>,
) -> (String, Option<String>)

Returns (account_id, dir) — account_id is always populated (even on a dir-resolution failure, so the caller can still log/track it); dir is None on the same gate/registry/fs failures compute_and_ensure_bundle_dir treats as soft failures — never abort auth.start over a config-dir issue.