fix: clamp SVG rect height to prevent negative values in waveform decoration

Math.sin() * 20 can produce -20, making the total height negative when
Math.random() contribution is small. SVG rect doesn't accept negative
height values, causing console errors.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: naomiaro

website/src/pages/examples/index.tsx

@@ -161,7 +161,7 @@ const WaveformDecoration: React.FC<{ className?: string }> = ({ className }) =>
       </linearGradient>
     </defs>
     {[...Array(40)].map((_, i) => {
-      const height = 10 + Math.sin(i * 0.5) * 20 + Math.random() * 15;
+      const height = Math.max(2, 10 + Math.sin(i * 0.5) * 20 + Math.random() * 15);
       return (
         <rect
           key={i}