fix(deps): update react monorepo to v19 (major)

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This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@types/react (source)	^18.3.12 -> ^19.0.3
@types/react-dom (source)	^18.3.1 -> ^19.0.2
react (source)	^18.3.1 -> ^19.0.0
react-dom (source)	^18.3.1 -> ^19.0.0

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Release Notes

facebook/react (react)

v19.0.0

Compare Source

facebook/react (react-dom)

v19.0.0

Compare Source

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[bluwy]

It doesn't look like React 19 is properly working in Astro yet.

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[bluwy]

The tests are failing as there's a pickle with how our tests runs and how tolerant React 19 is. In our tests, we run build and dev tests one after the other. The issue is that sometimes we import react or react-dom/server and it can give either the dev or prod version depending on process.env.NODE_ENV. However, if we import it once during production builds and get the production variant, we can't import it during dev again and get the development variant. Because imports are cached.

In practice I believe this is an issue for most frameworks including React 18, but they're tolerant enough that mismatching variants, e.g. react-dom/server (prod) + react/jsx-dev-runtime (dev) were fine. Overall I'm not really sure I to solve this yet that doesn't require rewriting our tests.

[ematipico]

Because imports are cached.

Is this caused by the fact that we run all our tests in the same process, in one single file? Can we try with --parallel?

[bluwy]

I don't think that would fix it. We'd have to split our build and dev tests as separate files so that each runs in their own process with their own import cache. I'm testing locally by running node ./packages/astro/0-css.test.js where its last test is failing because the HTML output got cut off due to React errors in @astrojs/react/server.js check() call. (you can add a log here where actual React components are erroring)