Function read_admin_ids 

pub fn read_admin_ids(
    admin_root: &Path,
) -> Result<BTreeSet<String>, WorktreeCopyError>

What: The administrative directory names under a common worktree-administration root. Why: A missing directory means no linked worktree has ever been registered, so it is an empty set rather than a failure.

In TS you’d write (pseudocode):

async function readAdminIds(adminRoot: string): Promise<ReadonlySet<string>>;