ACE fails if :root { color-scheme: light dark; } is used

:root {
color-scheme: light dark;
}

It makes Ace confused about color contrast. It compares the default colors against a white background, not a black one.

No file or test is named in the issue. Start by reproducing the example with `:root { color-scheme: light dark; }` and trace the color-contrast handling that selects the comparison background. Done means the default colors are compared against the appropriate dark background as well as the light one, with the reported confusion resolved.

Written by the indexing model from the issue text.