fix(palette-picker): hide in mobile top bar via media query

The component already returns null for mobile={true} (drawer), but
Docusaurus also renders right-side navbar items in the collapsed mobile
top bar without that prop. Hide .root below 996px to match Docusaurus's
own navbar collapse breakpoint.

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

Author: sserrata

demo/src/components/PalettePicker/styles.module.css

@@ -102,3 +102,10 @@
   flex-shrink: 0;
   color: var(--ifm-color-primary);
 }
+
+/* Hide in the mobile top bar — Docusaurus collapses the navbar at 996px */
+@media (max-width: 996px) {
+  .root {
+    display: none;
+  }
+}