fix(mosaic): open the gap between a panel title and its sections to space-6

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: maxyinger

packages/mosaic/src/components/panel/panel.styles.ts

@@ -4,7 +4,7 @@ import { colorVars, radiusVars, space } from '../../tokens.stylex';
 
 export const styles = stylex.create({
   root: {
-    gap: space['4'],
+    gap: space['6'],
     display: 'flex',
     flexDirection: 'column',
   },