MPRouteGeometry

Pure, engine-neutral route geometry shared by the DirectionsRenderer implementations in the Mapbox and Google adapters and by MPDirectionsRenderer. No map-engine types, so it is JVM-unit-testable; each adapter maps MPPoint results to its native point type.

Declared public (not internal): the adapters are separate Gradle modules, so Kotlin internal would not cross the module boundary. Same rationale as MPDirectionsRenderer.computeAnimationDurationMs. Not part of the documented public API.