search: replace Fuse.js with Pagefind (Default UI) + full UI polish

Remove the legacy Fuse.js search from html-head.html (it double-loaded
with the new Pagefind UI; backup kept at html-head.html.bkup) and add a
Pagefind Default-UI partial (search.html) injected into the sidebar via
menu.html.

Index scoping: tag the article element with data-pagefind-body in
baseof.html, term.html, and posts/{single,list}.html so Pagefind indexes
page content only (pages without the tag are skipped; 404.html stays
untagged).

search.html (all overrides #search-scoped, since pagefind-ui.css loads in
<body> after the head CSS):
  - compact input/magnifier/clear-button fitted to the sidebar; clear
    button uses fixed px (not %) because the results drawer is an in-flow
    child of the form, which stretches the form to results height
  - hide the empty .result-thumb placeholder (no images in the index) that
    was pushing result text ~90px right
  - restyle matched-term <mark> from UA yellow to subdued slate
  - keyboard navigation (Pagefind 1.5.2 has none; stock Enter is a silent
    no-op): capture-phase keydown implements ArrowUp/Down highlighting with
    wraparound across top-level hits AND their nested sub-results (each sub
    highlights its own .result-nested row), Enter opens the highlighted
    result (or the top result), and a fingerprint-aware MutationObserver
    keeps the highlight across Pagefind's async re-renders without
    resetting it on every DOM patch

themes/hugo-book/layouts/_partials/docs/html-head.html

@@ -32,13 +32,8 @@ https://github.com/alex-shpak/hugo-book
 {{- $styles := resources.Get "book.scss" | resources.ExecuteAsTemplate "book.scss" . | css.Sass | resources.Minify | resources.Fingerprint }}
 <link rel="stylesheet" href="{{ partial "docs/links/resource-precache" $styles }}" {{ template "integrity" $styles }}>
 
-<!-- Search -->
+<!-- Search: handled by Pagefind (see _partials/docs/search.html, injected into the
-{{- if default true .Site.Params.BookSearch -}}
+     sidebar via menu.html). The legacy Fuse.js search was removed to avoid double-loading. -->
-  {{- $searchJSFile := printf "%s.search.js" .Language.Lang }}
-  {{- $searchJS := resources.Get "search.js" | resources.ExecuteAsTemplate $searchJSFile . | resources.Minify | resources.Fingerprint }}
-  <script defer src="{{ "fuse.min.js" | relURL }}"></script>
-  <script defer src="{{ partial "docs/links/resource-precache" $searchJS }}" {{ template "integrity" $searchJS }}></script>
-{{ end -}}
 
 <!-- Service Worker -->
 {{- if .Site.Params.BookServiceWorker -}}

themes/hugo-book/layouts/_partials/docs/html-head.html.bkup

@@ -0,0 +1,60 @@
+{{ "<!--" | safeHTML }}
+Made with Book Theme
+https://github.com/alex-shpak/hugo-book
+{{ "-->" | safeHTML }}
+
+<meta charset="UTF-8">
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<meta name="description" content="{{ or .Description .Summary | plainify | htmlUnescape }}">
+<meta name="theme-color" media="(prefers-color-scheme: light)" content="#ffffff">
+<meta name="theme-color" media="(prefers-color-scheme: dark)" content="#343a40">
+<meta name="color-scheme" content="light dark">
+
+{{- with .Page.Params.BookHref -}}
+  <meta http-equiv="Refresh" content="0; url='{{ . }}'" />
+{{- end -}}
+
+{{ partial "opengraph.html" . }}
+{{ partial "schema.html" . }}
+
+<title>{{ partial "docs/html-head-title" . }}</title>
+{{ partial "docs/html-head-favicon" . }}
+
+{{- $manifest := resources.Get "manifest.json" | resources.ExecuteAsTemplate "manifest.json" . }}
+<link rel="manifest" href="{{ $manifest.RelPermalink }}">
+<link rel="canonical" href="{{ .Permalink }}">
+
+{{- range .Translations }}
+  <link rel="alternate" hreflang="{{ default .Site.LanguageCode .Language.Lang }}" href="{{ .Permalink }}" title="{{ partial "docs/title" . }}">
+{{- end -}}
+
+<!-- Theme stylesheet, you can customize scss by creating `assets/custom.scss` in your website -->
+{{- $styles := resources.Get "book.scss" | resources.ExecuteAsTemplate "book.scss" . | css.Sass | resources.Minify | resources.Fingerprint }}
+<link rel="stylesheet" href="{{ partial "docs/links/resource-precache" $styles }}" {{ template "integrity" $styles }}>
+
+<!-- Search -->
+{{- if default true .Site.Params.BookSearch -}}
+  {{- $searchJSFile := printf "%s.search.js" .Language.Lang }}
+  {{- $searchJS := resources.Get "search.js" | resources.ExecuteAsTemplate $searchJSFile . | resources.Minify | resources.Fingerprint }}
+  <script defer src="{{ "fuse.min.js" | relURL }}"></script>
+  <script defer src="{{ partial "docs/links/resource-precache" $searchJS }}" {{ template "integrity" $searchJS }}></script>
+{{ end -}}
+
+<!-- Service Worker -->
+{{- if .Site.Params.BookServiceWorker -}}
+  {{- $swJS := resources.Get "sw-register.js" | resources.ExecuteAsTemplate "sw.js" . | resources.Minify | resources.Fingerprint }}
+  <script defer src="{{ $swJS.RelPermalink }}" {{ template "integrity" $swJS }}></script>
+{{ end -}}
+
+{{ partial "google_analytics.html" . }}
+
+<!-- RSS -->
+{{- with .OutputFormats.Get "rss" -}}
+  {{ printf `<link rel="%s" type="%s" href="%s" title="%s" />` .Rel .MediaType.Type .Permalink $.Site.Title | safeHTML }}
+{{ end -}}
+
+{{- define "integrity" -}}
+  {{- if (urls.Parse .Permalink).Host -}}
+    integrity="{{ .Data.Integrity }}" crossorigin="anonymous"
+  {{- end -}}
+{{- end -}}

themes/hugo-book/layouts/_partials/docs/search.html

@@ -1,10 +1,184 @@
 {{ if default true .Site.Params.BookSearch }}
 <link href="/pagefind/pagefind-ui.css" rel="stylesheet">
 <script src="/pagefind/pagefind-ui.js"></script>
+<style>
+  /* Pagefind Default UI -> fit the sidebar. The #search id prefix gives id+class
+     specificity that beats pagefind-ui.css's class-only rules no matter where that
+     stylesheet loads (it loads in <body>, after the head CSS). */
+  #search .pagefind-ui__search-input { font-size: 0.85em; height: 2.4em; min-height: 2.4em; padding: 0 2.6em 0 2.4em; }
+  /* Magnifier: re-center it in the shrunken input; input padding-left 2.4em clears
+     the icon's right edge. */
+  #search .pagefind-ui__form:before { top: 7px; left: 12px; width: 14px; height: 14px; }
+  /* Fade the magnifier out while the input has content (no :has() -> icon stays). */
+  #search .pagefind-ui__form:has(.pagefind-ui__search-input:not(:placeholder-shown)):before { opacity: 0; }
+  /* Clear button: the form is the absolute containing block and in 1.5.2 the results
+     drawer is an in-flow child of it, so the form grows to the full results height —
+     use fixed dimensions keyed to the INPUT (form top == input top). */
+  #search .pagefind-ui__search-clear { top: 3px; right: 3px; height: 23px; font-size: 11px; padding: 0 6px; }
+  /* Results clipping: stack the drawer, allow shrink in the narrow sidebar. */
+  #search .pagefind-ui__drawer { flex-direction: column; gap: 0.4em; }
+  #search .pagefind-ui__results-area { min-width: 0; }
+  #search .pagefind-ui__result-excerpt { min-width: 0; }
+  /* No images exist in this index, but Pagefind still renders an 81px empty
+     .result-thumb on the left of every row, pushing the text ~90px right (the
+     "right-justified" look). Hide it so results fill the pane from the left. */
+  #search .pagefind-ui__result-thumb { display: none; }
+  #search .pagefind-ui__result-title,
+  #search .pagefind-ui__result-link  { font-size: 1em; overflow-wrap: anywhere; }
+  #search .pagefind-ui__result-excerpt{ font-size: 0.88em; overflow-wrap: anywhere; word-break: break-word; }
+  #search .pagefind-ui__message       { font-size: 0.8em; }
+  /* Keyboard-navigation highlight. Must be unmistakable on the dark theme
+     (bg #000, text #EEE): a solid slate fill + a bright 2px inset outline + white,
+     bold text. The class is applied to ONE node per selection: a sub's
+     .result-nested wrapper, or a top hit's .result-title line (see rowFor()). */
+  #search .pf-kbd-selected {
+    background: rgba(100,116,139,0.5);
+    outline: 2px solid #cbd5e1;
+    outline-offset: -2px;
+    color: #ffffff;
+    border-radius: 4px;
+  }
+  #search .pf-kbd-selected,
+  #search .pf-kbd-selected .pagefind-ui__result-title,
+  #search .pf-kbd-selected .pagefind-ui__result-link {
+    color: #ffffff;
+    font-weight: 600;
+  }
+  /* Matched-term <mark>: pagefind-ui.css resets `mark { all: revert }`, so matches
+     otherwise render the UA default harsh yellow. Restyle to a subdued slate on the
+     dark theme, scoped to the search results so page-content marks are untouched. */
+  #search .pagefind-ui__result mark {
+    background: rgba(100,116,139,0.45);
+    color: #ffffff;
+    border-radius: 2px;
+    padding: 0 1px;
+    font-weight: 600;
+  }
+</style>
 <div id="search"></div>
 <script>
     window.addEventListener('DOMContentLoaded', (event) => {
-        new PagefindUI({ element: "#search", showSubResults: true });
+        new PagefindUI({
+            element: "#search",
+            showSubResults: true,
+            focusOnSlash: true,     // press "/" anywhere to focus the search box
+            excerptLength: 20       // shorter excerpts fit the narrow sidebar
+        });
+
+        // --- Keyboard navigation (Pagefind Default UI 1.5.2 has none) ---
+        // ArrowDown/ArrowUp move a highlight over the result rows (wraparound,
+        // sub-result rows included — DOM order equals visual order); Enter opens the
+        // highlighted row, or the top result when nothing is highlighted. (Stock
+        // 1.5.2 Enter is a silent no-op — verified in the built pagefind-ui.js.)
+        //
+        // Two fixes over the naive version, both needed for a PHYSICAL keyboard:
+        //  (1) The link set is re-read from the LIVE DOM on every key press. Caching
+        //      a NodeList that Pagefind's async re-render later detaches means the
+        //      highlight/Enter act on a dead node and nothing appears.
+        //  (2) The MutationObserver reset is fingerprinted. Pagefind patches the
+        //      results subtree (excerpts, Svelte reactivity) right after a key press;
+        //      an unguarded childList observer would fire and clear the selection the
+        //      user just made. We only reset when the actual set of result hrefs
+        //      changes (a new query / rebuilt list), and otherwise re-assert the
+        //      highlight on the live row so a rebuilt <li> never loses it.
+        (function () {
+            var searchEl = document.getElementById('search');
+            if (!searchEl) return;
+            var SELECTED = 'pf-kbd-selected';
+            var index = -1;
+            var selFp = null; // fingerprint of the link set when we last applied a selection
+
+            function liveLinks() {
+                var resultsEl = searchEl.querySelector('.pagefind-ui__results');
+                if (!resultsEl) return [];
+                // Only interactive when actually rendered/visible. offsetParent is
+                // non-null here (it resolves to the form), but also accept a visible
+                // bounding box so a position:fixed sidebar can never null it out.
+                var visible = (resultsEl.offsetParent !== null) ||
+                              (resultsEl.getBoundingClientRect().height > 0);
+                if (!visible) return [];
+                return Array.from(searchEl.querySelectorAll('.pagefind-ui__results .pagefind-ui__result-link'));
+            }
+            function fp(links) {
+                return links.map(function (l) { return l.getAttribute('href'); }).join('\u0001');
+            }
+            function rowFor(link) {
+                if (!link.closest) return null;
+                // Sub-results: highlight this sub's OWN wrapper block, so each
+                // sub-topic (e.g. hacking -> anonymity / osint / courses) gets its
+                // own row rather than all of them re-lighting the parent <li>.
+                var nested = link.closest('.pagefind-ui__result-nested');
+                if (nested) return nested;
+                // Top-level hit: highlight just its title line. Highlighting the
+                // whole .pagefind-ui__result would also swallow its nested subs.
+                return link.closest('.pagefind-ui__result-title') ||
+                       link.closest('.pagefind-ui__result');
+            }
+            function clearAll() {
+                // The class can sit on a .result-nested, a .result-title, or a
+                // .result — clear it wherever it landed.
+                searchEl.querySelectorAll('.' + SELECTED)
+                    .forEach(function (r) { r.classList.remove(SELECTED); });
+            }
+            function deselect() {
+                clearAll();
+                index = -1;
+                selFp = null;
+            }
+            function move(dir) {
+                var links = liveLinks();
+                var n = links.length;
+                if (!n) return;
+                index = index < 0 ? (dir > 0 ? 0 : n - 1) : (index + dir + n) % n;
+                clearAll();
+                var row = rowFor(links[index]);
+                if (row) {
+                    row.classList.add(SELECTED);
+                    row.scrollIntoView({ block: 'nearest' });
+                }
+                selFp = fp(links);
+            }
+
+            // Capture phase on #search so this runs BEFORE Svelte's bubbling
+            // keydown/submit handlers on the input.
+            searchEl.addEventListener('keydown', function (e) {
+                var input = searchEl.querySelector('.pagefind-ui__search-input');
+                if (e.target !== input) return;
+                if (e.key === 'ArrowDown' || e.key === 'ArrowUp') {
+                    if (!liveLinks().length) return; // no results yet: leave default alone
+                    e.preventDefault();
+                    move(e.key === 'ArrowDown' ? 1 : -1);
+                } else if (e.key === 'Enter') {
+                    var links = liveLinks();
+                    if (!links.length) return;
+                    // Use the highlighted row, unless the selection went stale (the
+                    // result set changed under us and the MO hasn't caught up yet).
+                    var stale = (index < 0 || index >= links.length) ||
+                                (selFp !== null && selFp !== fp(links));
+                    var href = stale
+                        ? links[0].getAttribute('href')
+                        : links[index].getAttribute('href');
+                    if (href) {
+                        e.preventDefault();
+                        e.stopPropagation();
+                        location.href = href;
+                    }
+                }
+            }, true);
+
+            // Keep the selection in sync with Pagefind re-renders without nuking it.
+            var mo = new MutationObserver(function () {
+                if (index < 0) return; // nothing selected -> nothing to keep in sync
+                var links = liveLinks();
+                if (fp(links) !== selFp) { deselect(); return; } // result set changed
+                // Same result set, but Svelte may have rebuilt the <li> nodes:
+                // re-assert the highlight on the live row at the current index.
+                clearAll();
+                var row = rowFor(links[index]);
+                if (row) row.classList.add(SELECTED);
+            });
+            mo.observe(searchEl, { childList: true, subtree: true });
+        })();
     });
 </script>
 {{ end }}

themes/hugo-book/layouts/baseof.html

@@ -87,7 +87,7 @@
 {{ end }}
 
 {{ define "main" }}
-  <article class="markdown book-article">
+  <article class="markdown book-article" data-pagefind-body>
     {{- .Content -}}
   </article>
 {{ end }}

themes/hugo-book/layouts/posts/list.html

@@ -1,6 +1,6 @@
 {{ define "main" }}
   {{ range sort .Paginator.Pages }}
-  <article class="book-post markdown">
+  <article class="book-post markdown" data-pagefind-body>
     <h2>
       <a href="{{ .RelPermalink }}">{{ partial "docs/title" . }}</a>
     </h2>

themes/hugo-book/layouts/posts/single.html

@@ -1,5 +1,5 @@
 {{ define "main" }}
-<article class="markdown book-post">
+<article class="markdown book-post" data-pagefind-body>
   <h1>
     {{ partial "docs/title" . }}
   </h1>

themes/hugo-book/layouts/term.html

@@ -1,6 +1,6 @@
 {{ define "main" }}
   {{ range sort .Paginator.Pages }}
-  <article class="markdown book-post">
+  <article class="markdown book-post" data-pagefind-body>
     <h2>
       <a href="{{ .RelPermalink }}">{{ partial "docs/title" . }}</a>
     </h2>