/// How `AnalyzeBuilder::start()` handles a per-entry error mid-walk
/// (e.g. a permission-denied subdirectory, or a symlink loop under
/// `.follow_symlinks(true)`).
///
/// Deliberately a smaller enum than `planner::ErrorStrategy` rather than
/// reusing it: analysis never writes anything, so `Undo` has no meaning
/// here, and `ErrorStrategy` lives behind the `operations` feature,
/// which `analyze` doesn't require.