smooth-scroll on hash nav

Anchor links like /#bundles, /#revitalize, /#about now smooth-scroll
to their target instead of jumping. Reverts the earlier instant-jump
choice — for the homepage nav, the animation is the desired feedback.

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

src/router/index.js

@@ -166,7 +166,7 @@ const router = createRouter({
   // not honoured so users land at a predictable position rather than
   // wherever they last scrolled to.
   scrollBehavior(to) {
-    if (to.hash) return { el: to.hash }
+    if (to.hash) return { el: to.hash, behavior: 'smooth' }
     return { top: 0 }
   },
 })