Function is_effectively_minimized 

pub fn is_effectively_minimized(node: &LayoutNode) -> bool

True when a node renders as minimized: a locked leaf, or a branch whose every child is effectively minimized (a stacked chip strip). Mirrors isEffectivelyMinimized in frontend/layout/lib/layoutInvariants.ts. Reducer guards use THIS (not is_node_locked): a fully-collapsed branch has no branch-level marker in the display-mode model, but its stored size becomes load-bearing again the moment a child restores — so it must be just as untargetable as a minimized leaf.