Function execute_plans 

pub fn execute_plans<'a, I>(
    root: &'a Path,
    plans: I,
) -> ExecutePlans<'a, <I as IntoIterator>::IntoIter> 
where
    I: IntoIterator<Item = &'a GenerationPlan>,

Returns a lazy executor that runs plans in iterator order against root.

This is the canonical multi-plan sequential seam: each plan observes import bytes left on disk by earlier writes in the same pass. Production boxology generate and one-pass convergence proofs both drive this iterator so generate-all-before-write refactors cannot slip past them. After the first execution error the iterator is terminal and yields None forever, so later plans are neither executed nor written.