D22 — Router as a callback in router-in-the-loop placement

Decision

Router-in-the-loop and ECO take the router as a callback (RouteFn) and accept a placement only if it leaves fewer connections unrouted (ties: shorter HPWL for seeds only)

Alternatives

Link tm::route into tm::place; accept on estimated overflow

Reason

Keeps tm::place independent of the router and testable with a synthetic router; the router's verdict, not an estimate, decides (rule 4)