Function createSystemColorVars

createSystemColorVars(
colors: Partial<Record<IColor.Named, string>>,
): Record<string, string>
Builds --sxl-sys-color-* CSS variable overrides from a partial set of IColor.Named system colors, so that system/auto colors (which IColor.toCSS() emits as var(--sxl-sys-color-*)) resolve to the provided values rather than the global host mapping.
Parameters
- colors: Partial<Record<IColor.Named, string>>
Returns Record<string, string>

Remarks
Used by the grid container (SheetElement) and by UI rendered outside the grid subtree that must still match the grid's light/dark intent — most notably a color picker popup, which is portaled and would otherwise inherit the host's --sxl-sys-color-* (e.g. a light grid in a dark host would show the host's dark auto color). Names are lower-cased to match the variable IColor.toCSS() references; centralizing that here keeps callers from drifting.