Fastify + Vite + Svelte with SSR + full page hydration

I'm still working on this.

This is a quick (and dirty) proof of concept on how to hook up the different parts to make this work.

Every page renders in SSR and then hydrates the full page. In a previous version I hacked a partial hydration (islands) solution but it was too rudimentary. You can check the islands branch if you're interested.