Function fold_aware_visible_end_of 

pub fn fold_aware_visible_end_of(
    folds: &[Fold],
    foldenable: bool,
    scroll: u32,
    height: u32,
    total_lines: u32,
) -> u32

fold_aware_visible_end from a raw fold slice, skipping the FoldIndex build when there is no closed fold to walk over — the overwhelmingly common case, and one that runs per worker tick.