feat: improve code page scroll to top

Author: btea

app/pages/package-code/[[org]]/[packageName]/v/[version]/[...filePath].vue

@@ -256,6 +256,10 @@ function scrollToTop() {
     contentContainer.value.scrollTo({ top: 0, behavior: 'smooth' })
   }
 }
+const { y } = useScroll(contentContainer)
+const isVisible = computed(() => {
+  return y.value > SCROLL_TO_TOP_THRESHOLD
+})
 
 // Canonical URL for this code page
 const canonicalUrl = computed(() => `https://npmx.dev${getCodeUrl(route.params)}`)
@@ -459,6 +463,7 @@ defineOgImageComponent('Default', {
             </div>
             <div class="flex items-center gap-2">
               <button
+                v-if="isVisible"
                 type="button"
                 class="px-2 py-1 font-mono text-xs text-fg-muted bg-bg-subtle border border-border rounded hover:text-fg hover:border-border-hover transition-colors items-center inline-flex gap-1"
                 @click="scrollToTop"