feat(ui): implement refreshed UX for Composer layout (#21212)

Co-authored-by: Keith Guerin <keithguerin@gmail.com>

packages/cli/src/ui/components/shared/HorizontalLine.tsx

@@ -10,10 +10,12 @@ import { theme } from '../../semantic-colors.js';
 
 interface HorizontalLineProps {
   color?: string;
+  dim?: boolean;
 }
 
 export const HorizontalLine: React.FC<HorizontalLineProps> = ({
   color = theme.border.default,
+  dim = false,
 }) => (
   <Box
     width="100%"
@@ -23,5 +25,6 @@ export const HorizontalLine: React.FC<HorizontalLineProps> = ({
     borderLeft={false}
     borderRight={false}
     borderColor={color}
+    borderDimColor={dim}
   />
 );