fix(wiki): Header in die Inhaltsspalte → Titel fluchtet mit dem Text

Header war volle (schmalere, zentrierte) Inhaltsbreite, die zweispaltige Fläche
darunter aber breiter → Titel versetzt. Header jetzt in .wiki-page, Oberkante
mit der Seitenleiste gleichgezogen (margin-top:0).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

layouts/wiki/list.html

@@ -1,12 +1,11 @@
 {{ define "main" }}
-  <header class="section-header">
-    <h1 class="section-title">{{ .Title }}</h1>
-  </header>
-
   <div class="wiki">
     <aside class="wiki-side">{{ partial "wiki-nav.html" . }}</aside>
 
     <div class="wiki-page">
+      <header class="section-header">
+        <h1 class="section-title">{{ .Title }}</h1>
+      </header>
       <div class="single-content">{{ .Content }}</div>
 
       {{ $pages := where site.RegularPages "Section" "wiki" }}

layouts/wiki/single.html

@@ -1,14 +1,14 @@
 {{ define "main" }}
-  <header class="section-header">
-    <p class="section-rubric">{{ with .Params.group }}{{ . }}{{ else }}Wiki{{ end }}</p>
-    <h1 class="section-title">{{ .Title }}</h1>
-    {{ with .Params.summary }}<p class="section-description">{{ . }}</p>{{ end }}
-  </header>
-
   <div class="wiki">
     <aside class="wiki-side">{{ partial "wiki-nav.html" . }}</aside>
 
     <div class="wiki-page">
+      <header class="section-header">
+        <p class="section-rubric">{{ with .Params.group }}{{ . }}{{ else }}Wiki{{ end }}</p>
+        <h1 class="section-title">{{ .Title }}</h1>
+        {{ with .Params.summary }}<p class="section-description">{{ . }}</p>{{ end }}
+      </header>
+
       {{ $hasToC := .Params.toc | default false }}
       {{ $headers := findRE "<h[2-6]" .Content }}
       {{ if and $hasToC (ge (len $headers) 2) }}