#sprint-candidate

I recommend renaming client.css to hydration.css, since it's part of the hydration library, not the client library. Note that the hydration library is independent of UI framework, whereas the client library is specific to Preact.

Also, as part of this issue, can we add header: true to the astro.hydration library, similar to how we do for the xb-ui library? That will ensure that the <astro-*> custom elements begin in an upgraded state, reducing layout shift on the actual site, and possibly also helping with 🐛 Overlay and iFrame flicker on updating props values Active while editing within XB.