3. Visit once online so the worker installs. In DevTools › Application › Cache Storage delete **only** `staircase-assets-<hash>`, leaving the worker and `staircase-shell-<hash>`. Go offline and reload: "Step is napping" (`offline.html`), rather than the browser's error page or Staircase's own loading screen with nothing behind it. Back online, the page goes by itself and the app loads, rebuilding the asset cache.
`app-web/e2e/pwa.mjs` walks that path, and the pull request's own Verify carries this wording.