fix: avoid externalising node:async_hooks for the browser

[teemingc]

Accidentally introduced in #16198 because our shared exports now transitively imports a file that should only run on the server. Can be reproduced by building any of our test apps that import from @sveltejs/kit and you'll see an "externalized for browser" warning for the client build.

This PR marks the als import call as pure so it can be treeshaken correctly from the client code but we remove the pure annotation for server builds to keep it. Not proud of how hacky this is and am open to alternatives.

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[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from d5480d5:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/d5480d538218ce40da2a85e7c94bb566249e10a0

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16231

[changeset-bot]

🦋 Changeset detected

Latest commit: d5480d5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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@sveltejs/kit	Patch

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[teemingc]

Unused

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-16231-svelte.vercel.app/

[dummdidumm]

Would wrapping the dynamic import with if (!BROWSER) { ... } from esm-env work, too?

[teemingc]

Would wrapping the dynamic import with if (!BROWSER) { ... } from esm-env work, too?

Tried that but unfortunately it doesn't work 😞 it might in the future? Rolldown still has some treeshaking issues so it's not on par with Rollup

[dummdidumm]

Another idea (not sure if it's better): Make @sveltejs/kit/internal return a different file on the server/browser, i.e. on the browser it returns a noop basically for try_get_request_store.