attempt to fix dev mode FOUC

[Rich-Harris]

Alternative to #1026. It seems to work for apps once they're running, but the first load after the server starts always results in this:

I have no idea why — @dominikg does this look familiar?

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[dominikg]

Source for that error:
https://github.com/sveltejs/vite-plugin-svelte/blob/46c27500e10aa97dd8ff6a5d6fc80d110c36cdc8/packages/vite-plugin-svelte/src/index.ts#L195

I think whats happening is that there are 2 caches for svelte compile data and the css is only checked in one. It gets added to the ssr cache during ssr render pass, but when the browser requests the css via the injected link, its a client request and transform is called with ssr=false. -> cache miss for the module css and error.

[Rich-Harris]

closing in favour of #1057