doc-navigation: skip sidebar anchor-only entries from Prev/Next walk

`#host` and `#lxc-net` are visual sidebar section headers for the
Storage Share Manager page — they group their submenu items in the
sidebar tree but point back at the parent Overview with an anchor,
so they aren't standalone docs the reader advances to. Including
them in the flat Previous/Next sequence produced two regressions:

* On `/docs/storage-share/#host` the Next button targeted `#host`
  again, so clicking it didn't move. The earlier hash-tracking fix
  intended to catch this, but a `useEffect` with an empty dep array
  only runs on mount — and Next.js Link navigations don't fire
  `hashchange` when the path changes too, so a cross-page navigation
  that lands on `#host` (sidebar click) rendered with hash="" and
  re-collapsed to the section header.
* On `/docs/storage-share/lxc-mount-points/` the Next button pointed
  at `#lxc-net` instead of advancing to `lxc-nfs-client`, since the
  section header sat between the two real pages in the flat list.

Filter out any sidebar entry whose href contains `#` at walk time so
the flat list only carries real pages. With them gone, an anchored
URL collapses to its parent Overview and Next walks straight into
the first subpage. The hash effect + state are no longer needed so
the component drops them, keeping only the pathname-based match.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/components/ui/doc-navigation.tsx

@@ -9,7 +9,6 @@
 import { Link, usePathname } from "@/i18n/navigation"
 import { ChevronLeft, ChevronRight } from "lucide-react"
 import { useTranslations } from "next-intl"
-import { useEffect, useState } from "react"
 import { sidebarItems } from "@/components/DocSidebar"
 
 interface DocNavigationProps {
@@ -31,6 +30,21 @@ interface FlatPage {
   sectionI18nKey?: string
 }
 
+// Sidebar entries whose href contains a fragment (`#host`, `#lxc-net`,
+// …) are visual section headers that group submenu items inside an
+// existing physical page (currently only Storage Share Manager uses
+// this pattern — `Host storage integration` and `LXC network sharing`
+// are headers for groups of subpages, but their href is the parent
+// Overview page with an anchor). They aren't standalone docs the
+// reader can advance to, so including them in the Previous/Next walk
+// produces two regressions: on the page they anchor (`#host`) Next
+// circles back to the same URL, and on a regular page that happens to
+// sit next to one of them in the flat list (`lxc-mount-points`) Next
+// jumps to the section header instead of skipping to the next real
+// subpage. Skip them at walk time so both cases collapse to "the next
+// real page in reading order".
+const isAnchorOnlyHref = (href: string) => href.includes("#")
+
 function walkSubmenu(
   items: SubMenuItem[],
   section: string,
@@ -38,13 +52,15 @@ function walkSubmenu(
   out: FlatPage[],
 ) {
   items.forEach((sub) => {
-    out.push({
-      title: sub.title,
-      i18nKey: sub.i18nKey,
-      href: sub.href,
-      section,
-      sectionI18nKey,
-    })
+    if (!isAnchorOnlyHref(sub.href)) {
+      out.push({
+        title: sub.title,
+        i18nKey: sub.i18nKey,
+        href: sub.href,
+        section,
+        sectionI18nKey,
+      })
+    }
     if (sub.submenu && sub.submenu.length > 0) {
       walkSubmenu(sub.submenu, section, sectionI18nKey, out)
     }
@@ -56,26 +72,6 @@ export function DocNavigation({ className }: DocNavigationProps) {
   const tNav = useTranslations("docNav")
   const tSidebar = useTranslations("docSidebar")
 
-  // Capture the URL hash (`#host`, `#lxc-net`, …) on the client so we
-  // can disambiguate Previous/Next when a single doc page hosts several
-  // sidebar entries via in-page anchors (Storage Share Manager is the
-  // canonical case: /docs/storage-share + /docs/storage-share#host +
-  // /docs/storage-share#lxc-net are three distinct sidebar items but a
-  // single physical page; usePathname() returns the same string for
-  // all three because the fragment is not part of the path).
-  //
-  // SSR can't see the hash, so we hydrate with an empty string and
-  // refresh on mount + on hashchange. The brief render before
-  // hydration just shows the navigation as if the user were at the
-  // parent page — same behaviour as before this fix, so no regression.
-  const [hash, setHash] = useState("")
-  useEffect(() => {
-    const sync = () => setHash(window.location.hash || "")
-    sync()
-    window.addEventListener("hashchange", sync)
-    return () => window.removeEventListener("hashchange", sync)
-  }, [])
-
   const tItem = (i18nKey: string | undefined, fallback: string) => {
     if (!i18nKey) return fallback
     try {
@@ -89,7 +85,7 @@ export function DocNavigation({ className }: DocNavigationProps) {
     const flatItems: FlatPage[] = []
 
     sidebarItems.forEach((item) => {
-      if (item.href) {
+      if (item.href && !isAnchorOnlyHref(item.href)) {
         flatItems.push({ title: item.title, i18nKey: item.i18nKey, href: item.href })
       }
 
@@ -124,29 +120,14 @@ export function DocNavigation({ className }: DocNavigationProps) {
   const stripTrailingSlash = (s: string) => (s !== "/" ? s.replace(/\/+$/, "") : s)
   const normalizedPathname = stripTrailingSlash(pathname)
 
-  // Match attempt order:
-  //   1. pathname + hash (e.g. /docs/storage-share#host)  — exact match
-  //      against sidebar items that intentionally point to an in-page
-  //      anchor as the "current location" for navigation purposes.
-  //   2. pathname alone — the regular case, no anchor in the URL.
-  //
-  // Without step 1, every anchor visit collapsed to the parent page
-  // and Next/Previous walked from there — so on /docs/storage-share#host
-  // the bottom bar offered the same #host as Next (no movement) and on
-  // /docs/storage-share/lxc-mount-points/ Next pointed back at #host
-  // because the entire flat list got indexed from position 0.
-  const effectivePath = normalizedPathname + hash
-  let currentPageIndex = -1
-  if (hash) {
-    currentPageIndex = allPages.findIndex(
-      (page) => stripTrailingSlash(page.href) === effectivePath,
-    )
-  }
-  if (currentPageIndex === -1) {
-    currentPageIndex = allPages.findIndex(
-      (page) => stripTrailingSlash(page.href) === normalizedPathname,
-    )
-  }
+  // Anchored URLs (`/docs/storage-share/#host`) share their pathname
+  // with the Overview page, so they collapse to that page's flat-list
+  // index — Previous walks back into the previous section as usual and
+  // Next advances to the first real subpage (`host-nfs`) instead of
+  // looping back to the same anchor.
+  const currentPageIndex = allPages.findIndex(
+    (page) => stripTrailingSlash(page.href) === normalizedPathname,
+  )
 
   const prevPage = currentPageIndex > 0 ? allPages[currentPageIndex - 1] : null
   const nextPage = currentPageIndex < allPages.length - 1 ? allPages[currentPageIndex + 1] : null