How do you configure a route for lazy loading?

Tests route-level code splitting and initial bundle control in large SPAs. A strong answer covers: first, dynamic imports in router config so each route becomes its own chunk; second, on-demand fetching on first navigation instead of upfront; third, quantifying impact, like reducing a multi-megabyte bundle to a shell plus small chunks; fourth, contrasting with eager loading. Red flag: confusing lazy loading with image deferral or component tricks without addressing route-boundary code splitting.