next.js

31774433 - Make Instant Navigation Testing full-page loads work when deployed (#95222)

Make Instant Navigation Testing full-page loads work when deployed (#95222) This makes full-page loads work under the Instant Navigation Testing API on a deployment, not just under `next dev` and `next start`. With the API active, a full-page load (a reload, an MPA navigation, or direct URL entry) on a deployment failed with a minified React hydration error, and releasing the lock then hard-reloaded the page instead of resolving client-side. Client-side navigations under the lock already worked; the gap was full-page loads. The API works by injecting an inline script that sets `self.__next_instant_test`, which the client reads at `app-index` init as its hydration source. That read only happens on a full-page load; client-side navigations go through the segment cache and the lock and never read it. The script was previously injected at request time through a transform stream, which runs only when the function renders the document. On a deployed full-page load the browser instead parses the prebuilt static prelude served from the edge cache, which was prerendered without the cookie and so carried no script, leaving `self.__next_instant_test` undefined. When the testing API is enabled (in development, or in a production build via `experimental.exposeTestingApiInProductionBuild`), we embed the cookie-guarded bootstrap into the prerendered prelude through React's `bootstrapScriptContent`, so it lands in the cached static shell and runs before the client bootstrap module. That production-build flag is meant for protected preview environments, so a normal production build never embeds the script, and even where it is embedded it stays inert on requests without the instant-navigation cookie (the prelude is shared across all requests). The same content is folded into the dynamic render path in `renderToStream`, and the now-redundant request-time transform is removed.