Parse any CSS color (hex, rgb(), hsl()) and emit all three formats plus relative luminance. Compute WCAG contrast ratios

Parse any CSS color (hex, rgb(), hsl()) and emit all three formats plus relative luminance. Compute WCAG contrast ratios against a background with AA/AAA pass-fail for normal and large text, and lighten, darken, or mix colors. Built for agents generating accessible UI themes. POST a JSON body like: {"color":"#3498db","background":"#ffffff"}