'use cache' killed ISR

Before, one line at the top of a route: export const revalidate = 60. After, one line inside the function that owns the data: cacheLife('minutes'). The obvious reading is a rename. It is not. ISR gave a route with five data sources exactly one freshness contract. Product prices want 60 seconds, the nav menu wants a week, markdown wants forever, and the page has one dial. So we split routes…