A switcher is links
The language switcher above is two elements: an <a> and a <span> for the one you are
reading. No runtime, no island, no hydration.
It works because site.translate(path, "es") is an answer rather than a guess — the build
made every page before it rendered this one, so it knows the Spanish copy exists and where.
An island here would download a quarter of a megabyte to do what an anchor does.