Use new theme vars (#63)

This PR swaps the theme to use the new stuff from the Theme Studio

src-web/components/GrpcConnectionLayout.tsx

@@ -109,7 +109,7 @@ export function GrpcConnectionLayout({ style }: Props) {
             className={classNames(
               'x-theme-responsePane',
               'max-h-full h-full grid grid-rows-[minmax(0,1fr)] grid-cols-1',
-              'bg-background rounded-md border border-background-highlight',
+              'bg-surface rounded-md border border-border-subtle',
               'shadow relative',
             )}
           >