`experimental.useExperimentalReact` names the React *build* it pulls in
rather than the feature it's there for. Rename it to `blockingSSR` — the
actual capability (React's blocking SSR, which emits `<link
rel="expect">` to hold first paint until the streamed shell is coherent)
— mirroring React's own feature flag so it's clear why the experimental
channel got enabled when grepping.
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Jude Gao