Descendant selector fails if outer element is not top-level

[Rich-Harris]

REPL:

<div>
  <p>
    <span>styled</span>
  </p>
</div>

<style>
  p span {
    color: red;
  }
</style>

The <p> element is not given the svelte-xyz attribute (but the <div> is, unnecessarily).