feat(theme): ignore inner-page items in next/prev link

Next/prev links should jump to a separate page.  This would be spoiled
by inner-page links with hashes, so jump over them.

src/client/theme-default/composables/prev-next.ts

@@ -8,7 +8,13 @@ export function usePrevNext() {
 
   return computed(() => {
     const sidebar = getSidebar(theme.value.sidebar, page.value.relativePath)
-    const candidates = getFlatSideBarLinks(sidebar)
+    const links = getFlatSideBarLinks(sidebar)
+
+    // ignore inner-page links with hashes
+    const candidates = uniqBy(
+      links,
+      (link) => link.link.substring(0, link.link.lastIndexOf('#')) || link.link
+    )
 
     const index = candidates.findIndex((link) => {
       return isActive(page.value.relativePath, link.link)
@@ -61,3 +67,11 @@ export function usePrevNext() {
     }
   })
 }
+
+function uniqBy<T>(array: T[], keyFn: (item: T) => any): T[] {
+  const seen = new Set()
+  return array.filter((item) => {
+    const k = keyFn(item)
+    return seen.has(k) ? false : seen.add(k)
+  })
+}