Function normalize_user_path 

pub fn normalize_user_path(path: &Path) -> PathBuf

Tilde-expand + absolutise a user-typed path. ~/rest → $HOME/rest; ~ alone → $HOME; relative paths join the current working directory. Phase 5.8.AA.j: hoisted from lattice-ui-tui::app::normalize_user_path so the host-side do_edit migration can reach it without dragging in the App.