The single entry: resolve --sxl-* vars for a mode, with any number of partial overrides merged over
the default theme (later wins). A surface is just an overrides partial — e.g. grid-react's
GRID_SURFACE[mode] — so themeVars(mode, GRID_SURFACE[mode]) yields the grid surface, and a client's
brand tweak is one more partial: themeVars(mode, GRID_SURFACE[mode], { 'color-accent': 'purple' }).
The single entry: resolve
--sxl-*vars for a mode, with any number of partial overrides merged over the default theme (later wins). A surface is just an overrides partial — e.g. grid-react'sGRID_SURFACE[mode]— sothemeVars(mode, GRID_SURFACE[mode])yields the grid surface, and a client's brand tweak is one more partial:themeVars(mode, GRID_SURFACE[mode], { 'color-accent': 'purple' }).