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>

layouts/index.html

@@ -0,0 +1,41 @@
+{{ define "main" }}
+  {{ .Content }}
+
+  {{ $library := where site.RegularPages "Section" "library" }}
+  {{ $journal := first 20 $library.ByDate.Reverse }}
+
+  <section class="journal" aria-label="Journal — neueste Beiträge">
+    <header class="journal-header">
+      <h2>Journal</h2>
+      <p class="text-muted">Was zuletzt geschrieben wurde.</p>
+    </header>
+
+    <ol class="journal-list">
+      {{ range $journal }}
+        <li class="journal-entry">
+          <a class="journal-entry-link" href="{{ .RelPermalink }}">
+            <div class="journal-meta">
+              {{ with .Parent }}
+                <span class="journal-section">{{ .Title }}</span>
+              {{ end }}
+              <time class="journal-date" datetime="{{ .Date.Format "2006-01-02" }}">{{ .Date.Format "2006-01-02" }}</time>
+            </div>
+            <h3 class="journal-title">{{ .LinkTitle }}</h3>
+            {{ with .Params.summary }}
+              <p class="journal-summary">{{ . }}</p>
+            {{ end }}
+            {{ with .Params.tags }}
+              <ul class="journal-tags">
+                {{ range . }}<li>#{{ . }}</li>{{ end }}
+              </ul>
+            {{ end }}
+          </a>
+        </li>
+      {{ end }}
+    </ol>
+
+    {{ if gt (len $library) 20 }}
+      <p class="more"><a href="/library/">→ Alle Beiträge in der Library</a></p>
+    {{ end }}
+  </section>
+{{ end }}