Function heal_layout_body 

fn heal_layout_body(
    layout: &mut LayoutState,
    valid_blocks: &HashSet<&str>,
) -> (bool, Vec<String>)

Pure heal pass on a LayoutState given the set of block IDs that should still be present. Returns (changed, orphans_removed).

Collects orphans from both leaforder AND any leaf still reachable in rootnode — leaforder can drift out of sync with rootnode if a write was interrupted, and the heal is the last defense. Prunes each orphan via prune_block_from_layout, then clears focusednodeid if the rootnode ended up empty.