Phase 4 (Test): Update ~test-layout-full and ~test-detail-layout-full defcomps
to use ~root-header with env free variables. Switch render functions to
render_to_sx_with_env.
Phase 5 (Cart): Convert cart-page, cart-admin, and order render functions.
Update cart .sx layout defcomps to use ~root-header from free variables.
Phase 6 (Blog): Convert all 7 blog layouts (blog, settings, sub-settings x5).
Remove all root_header_sx calls from blog.
Phase 7 (Market): Convert market and market-admin layouts plus browse/product
render functions. Remove root_header_sx import.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>