D30 — Per-net coupled routing for detected USB pairs

Decision

Per-net coupled routing through RouterOptions::pair_nets (pairs routed coupled first when diff_pairs is off), filled from detected USB 2.0 D+/D- pairs with --component-rules soft or on

Alternatives

Name-based P/N detection only (--diff-pairs, all or nothing)

Reason

USB nets are often named DP/DM (not P/N or +/-); a three-line hook (pair_wanted) keeps the router change minimal while the router is being changed elsewhere