Function load_subagent_parent_worktree 

pub fn load_subagent_parent_worktree(
    child_session_id: &str,
) -> Result<Option<ManagedWorktree>>

The managed checkout of a sub-agent’s parent, or None when child_session_id is not a sub-agent or its parent owns no checkout. A child works in its parent’s checkout without owning it.