Function composite_weight 

fn composite_weight(
    pwc: &PathWithMetrics,
    hops: usize,
    params: WeightingParams,
) -> f64

Composite selection weight for a candidate path.

Refines pwc.cost (the EdgeValueFn output) with latency and capacity factors derived from the per-path aggregates. Factors are neutral (1.0) when the corresponding aggregate is unavailable to avoid penalising unprobed paths. For 0-hop routes (hops == 0) the capacity factor is always 1.0 — direct me -> dest packets use no payment channel, so capacity_floor = None is expected.