fix: prevent await_reactivity_loss in notify_version

[GauBen]

closes #16914

The fix was trivial, the test was painful to write and requied ai assistance

• runs in its own file to set DEV to true globally
• has a hand-written svelte component to reproduce the issue

The diff is big because I bumped svelte to latest

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[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from d044c80:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/d044c80dd9a202cafdfed37b087ce01d76608681

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16915

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Latest commit: d044c80

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

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[Nic-Polumeyv]

Awesome! It might be worth doing a bigger change in the future, since this is an issue in a few places that would need to be wrapped in untrack. I'm in favor of not using runes for internal bookkeeping, as that's really the root of the problem. We could also have the svelte compiler disarm at the expression boundary instead of queueing? I haven't looked into this enough, but we can circle back. Better to get @Rich-Harris opinion, not really my lane.

I am going to dismiss my review this in favor of sveltejs/svelte#18694.