Renders nothing for the first [delay] (default 200ms) of sustained
loading, then renders the [whileDelayed] child until loading completes.
Mirrors the web useDelayed hook so a fast network response doesn't
flash a skeleton.
Used in the next commit's home screen rewrite; otherwise unused this
slice.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
