fix: fix static screen params for Record-based configsi (#13119)

When static screens are built from a `Record<K, V>`, TypeScript can
widen the screen type to a union of all screen components. Our params
inference used a distributive conditional type, so TypeScript tried to
infer params separately for every screen in that union for each route.

With many prop-less screens, this created a huge intermediate union and
caused `useNavigation('ScreenName')` to fail with TS2590.

This changes the screen params lookup to treat the widened screen union
as one type instead of distributing over every screen.