fix(Provider): throw a clearer error when rendered in a React Server Component (#2082)

[veksa]

Closes #2082.

If you render <Provider> in a Server Component you currently get a pretty useless error. In React's react-server build the effect hooks just don't exist (useEffect/useLayoutEffect/useRef/useState are all undefined — only useMemo, use, useId and friends survive), so useIsomorphicLayoutEffect ends up undefined and you hit useIsomorphicLayoutEffect is not a function. Adding "use client" doesn't really help either — as noted in the issue, store/context aren't serializable so you just trade it for a different confusing error.

So this does what the thread landed on: an explicit dev-only check at the top of <Provider>, before any hook runs, that throws a message actually telling you what's wrong and to add "use client".

The "react-server" export condition already handles the normal Next.js case, but only when the bundler applies it to react-redux too. This is the fallback for the "and many others" setups where React resolves to its server build but we don't — and since every app renders <Provider>, that's a good enough place to catch it.

On testing (which came up in the thread): we don't need a real RSC environment. The whole thing hinges on useIsomorphicLayoutEffect being undefined, so the test just mocks it to undefined and checks <Provider> throws. Without the guard you'd get ... is not a function instead, which doesn't match, so the test really is hitting the new branch.

Kept it scoped to <Provider> — the hooks would blow up in RSC too, but the Provider is the earliest thing everyone renders.

Changes:

• src/components/Provider.tsx — the guard (dev only, stripped in prod)
• test/components/Provider-rsc.spec.tsx — new test, separate file so the module mock doesn't leak into the other Provider tests

[pkg-pr-new]

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commit: 3bc503b