Add site search (Pagefind)

Client-side index generated after the Hugo build; search box in the
header, results page with a section filter.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDRjtmAiNpo5mK5N3d7QwZ

layouts/baseof.html

@@ -18,8 +18,15 @@
       <a href="{{ .URL }}"{{ if or ($current.IsMenuCurrent .Menu .) ($current.HasMenuCurrent .Menu .) (eq $current.Section .Page.Section) }} class="active"{{ end }}>{{ .Name }}</a>
       {{ end }}
     </nav>
+    <form class="search" role="search" action="{{ "search/" | relURL }}" method="get">
+      <input type="search" name="q" placeholder="Search…" aria-label="Search the site">
+    </form>
   </header>
-  <main>
+  {{/* search index: content pages only (not lists), filterable by section; see layouts/search.html */}}
+  {{ $indexed := and .IsPage (ne .Layout "search") (ne .Params.tab "comments") }}
+  {{ $section := "" }}{{ with .FirstSection }}{{ if not .IsHome }}{{ $section = .Title }}{{ end }}{{ end }}
+  {{ if eq .Section "machine-tabs" }}{{ $section = "Museum" }}{{ end }}
+  <main{{ if $indexed }} data-pagefind-body{{ with $section }} data-pagefind-filter="Section:{{ . }}"{{ end }}{{ end }}>
     {{ block "main" . }}{{ end }}
   </main>
   <footer class="site-footer">