init: scaffold OPENBUREAU site with shibui-derived theme

- Hugo site for openbureau.ch (Deutsch, i18n-ready for EN/IT)
- Theme themes/openbureau/ = local copy of shibui, customized via
  site-level layouts and assets to keep the theme reference clean
- Editorial typography stack: Newsreader serif body, Space Grotesk
  display, Inter for listings, IBM Plex Mono for technical meta
- Content structure: library/ (Theorie, Büroführung, Software) with
  manifest and colophon at root; software is a library category, not
  a separate top-level
- Three views over one source: Journal (chronological home),
  Library (atlas grouped by section + tag cloud), single articles

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

themes/openbureau/layouts/_default/single.html

@@ -0,0 +1,55 @@
+{{ define "main" }}
+  {{ partial "terms.html" (dict "taxonomy" "tags" "page" .) }}
+
+  {{/* Table of Contents */}}
+  {{ $hasToC := .Params.toc | default true }}
+  {{ $headers := findRE "<h[2-6]" .Content }}
+  {{ if and $hasToC (ge (len $headers) 1) }}
+    <nav class="toc">
+      <strong>TABLE OF CONTENTS</strong>
+      <div class="toc-content">
+        {{ .TableOfContents }}
+      </div>
+    </nav>
+  {{ end }}
+
+  <!-- Content -->
+  {{ partial "list-to-carousel.html" .Content }}
+
+  <!-- Carousel CSS & JS -->
+  <link rel="stylesheet" href="/css/auto-carousel.css">
+  <script type="text/javascript" src="/js/auto-carousel.js"></script>
+
+  <div class="time">
+    {{ partial "date.html" .Date }}
+    {{ $showReadingTime := .Params.showreadingtime | default site.Params.showreadingtime | default true }}
+    {{ if and $showReadingTime .ReadingTime }}
+      <span class="reading-time"> · {{ .ReadingTime }} min read</span>
+    {{ end }}
+    {{ $showLastMod := .Params.showlastmod | default site.Params.showlastmod | default false }}
+    {{ if and $showLastMod .Lastmod }}
+      {{ if ne .LastMod.Format "2006-01-02" .Date.Format "2006-01-02" }}
+        <span class="lastmod"> · Last updated: {{ .LastMod.Format "2006-01-02" }}</span>
+      {{ end }}
+    {{ end }}
+  </div>
+
+  <!-- Comments block -->
+  {{ if and .Content (default true (default .Site.Params.comments
+    .Params.comments))
+  }}
+    <div class="comments">{{- partial "comments" . -}}</div>
+  {{ end }}
+
+  {{ if not .IsHome }}
+    <div class="terminal-nav">
+      <div class="back-nav">
+        {{ with .Parent }}
+          <a href="{{ .RelPermalink }}" class="back-link">../</a>
+        {{ else }}
+          <a href="{{ "/" | relURL }}" class="back-link">../</a>
+        {{ end }}
+      </div>
+    </div>
+  {{ end }}
+{{ end }}