feat(image): bump radius presets so S/M/L are actually visible on real images

4px and 8px were imperceptible on typical image sizes. New scale
0/8/16/32/50% gives visible steps for None/S/M/L and keeps Full as
round.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

craft/src/components/media/ImageBlock.tsx

@@ -160,7 +160,7 @@ const ImageBlockSettings: React.FC = () => {
     }
   }, [showBrowser]);
 
-  const radiusPresets = ['0', '4px', '8px', '16px', '50%'];
+  const radiusPresets = ['0', '8px', '16px', '32px', '50%'];
 
   const setPropStyle = useCallback((key: string, value: string | undefined) => {
     setProp((p: ImageBlockProps) => {