feat: automatically use React DOM browser for Suspense SSR - #4330

When useSWR suspends during SSR without data, SWR currently throws “Fallback data is required when using Suspense in SSR.” This change detects React DOM's Canary browser API and calls React.use(browser()) when available, allowing React to render the nearest Suspense fallback and fetch the data in the browser automatically.

No new configuration is required. Existing fallback/preloaded data continues to render on the server, and older runtimes retain the existing error. This also covers useSWRInfinite through the shared core hook. React DOM is an optional peer, with a React Native mapping that excludes it in Metro.

The E2E app uses Next.js 16.4.0-canary.19, which bundles React DOM 19.3.0-canary-f4e439e1-20260902 with the API.

Validation:

• SWR build and production Next.js build passed.
• Type checks, typing tests, lint, and formatting passed.
• 21 targeted SSR/Suspense unit tests and 3 browser tests passed.
• Browser coverage verifies server fallbacks with JavaScript disabled, client hydration without console errors, infinite queries, supplied data, and disabled keys.
• Metro resolver checks map React DOM to an empty module on iOS and Android.

React API reference: https://react.dev/reference/react-dom/browser