Function max_routable_par 

pub fn max_routable_par(
    mp: &Metapipeline,
    buffer_words: &[usize],
    ag_stages: &[usize],
    t: &PlasticineTarget,
    budget: LinkBudget,
) -> Result<(usize, usize), Unplaceable>

The widest unroll that fits t AND routes statically within budget — the routability-aware unroll (the static vector network’s perimeter ports, not PCU/PMU capacity, bound a DRAM-fed unroll first on a large mesh). Returns (routable, capacity); routable == 1 is reported even when a single instance exceeds the budget, so a row can still say routed_statically: false honestly.