The Multi-device windows (mac/mesh/control.html, windows/mesh/app.html,
linux/mesh/app.html) didn't load shared/ui-look.js, so General threw on
UI.themeRow and drew nothing. They load it now with ui-look.css, and the
mesh apps get General > Appearance the way one-to-one has it: setLook in
the preloads and IPC, state.look, the theme applied at start, and the
accent colour (and --accent-soft from it) in the window.

shared/test/page-scripts.js reads each control window's real script list:
every UI.x() its scripts call must be defined by one of them, and every
api.x() General calls must be in that window's preload.