A segmented Retail | Restaurant control in the register header flips the
location's service_style in place (RegisterController@setMode → pos.mode.set).
Switching to restaurant lands on the Floor and reveals Floor/Kitchen/Menu in the
sidebar; switching to retail stays on the register. Covered by PosRestaurantTest.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>