Surface Expo Router's ErrorBoundary and route-level errors #6160

Expo Router exports its own ErrorBoundary from each route file (see samples/expo/app/_layout.tsx: export { ErrorBoundary } from 'expo-router';). The SDK currently does nothing to capture errors that hit that boundary — users get the Expo Router fallback UI but Sentry only sees the error if the global error handler catches it. We also export Sentry.ErrorBoundary / withErrorBoundary but it's a generic React boundary, unrelated to Expo Router's per-route boundary.

Provide a wrapped ErrorBoundary re-export (e.g. Sentry.wrapRouterErrorBoundary or auto-wrapped when the integration loads) that:

• Captures the error with route context (route.name, route.path, route.params) attached.
• Marks the in-flight navigation transaction (if any) as errored.
• Adds a breadcrumb for the boundary fallback render.

Investigate whether the Metro/Babel plugin (tools/metroconfig.ts) can auto-instrument re-exports of ErrorBoundary from expo-router without requiring the user to change their code.