Implement the user-visible offline path for service-worker-controlled pages.
Scope:
- Allow the loader/e2e harness to simulate offline network failures deterministically.
- Support app-shell caching during install and serving cached HTML/CSS/JS/images while offline.
- Surface consistent errors when neither cache nor network can satisfy a request.
- Preserve redirects and response metadata when cached responses are replayed.
- Ensure reloads of controlled pages can be satisfied from Cache API responses without external network access.
Acceptance criteria:
- E2E scenario registers a worker, caches an app shell, reloads offline, and asserts DOM/console output from cached resources.
- Tests cover offline miss behavior, cached navigation responses, cached subresources, and network recovery.
- Any new harness network toggle is documented alongside the scenario DSL.