Request shaping and browser state

Top-level headers and request.headers are merged, then remove_headers is applied case-insensitively. Cookies work in both engines. Browser profiles support locale, timezone, viewport, scale, mobile/touch, color scheme, and user agent.

Local and session storage are installed before application scripts. Network profiles include offline, slow 3G, fast 3G, 4G, or bounded custom latency and throughput.