drop <main>, use <article role="main"> — bold landmark structure

body direct children: <nav>, <header>, <article role="main">, <footer>
- <nav>: site navigation (own landmark)
- <header>: page identity — title, author, date, metadata
- <article role="main">: content (screen reader gets landmark via role)
- <footer>: site footer

No <main> wrapper. Fewer tags, clearer signal.
Header block defined per-layout (prose gets eyebrow/date, docs gets hgroup).
Content block defined per-layout (docs adds sidebar <nav> + <aside> TOC).

layouts/index.html

@@ -1,32 +1,30 @@
 {{ define "title" }}{{ .Site.Title }}{{ end }}
 
-{{ define "main" }}
-  <main>
-    <article data-layout="prose">
-
-      <header>
-        <hgroup>
-          <h1>{{ .Site.Title }}</h1>
-          <p>{{ .Site.Params.description | default "An agent-first approach to web generation." }}</p>
-        </hgroup>
-      </header>
-
-      <section>
-        <h2>Recent</h2>
-        {{ range first 10 .Site.RegularPages }}
-        <article>
-          <header>
-            <h3><a href="{{ .Permalink }}">{{ .Title }}</a></h3>
-            <p data-text="dim">
-              <time datetime="{{ .Date.Format "2006-01-02" }}">{{ .Date.Format "January 2006" }}</time>
-              {{ with .Params.eyebrow }} · {{ . }}{{ end }}
-            </p>
-          </header>
-          {{ with .Summary }}<p>{{ . }}</p>{{ end }}
-        </article>
-        {{ end }}
-      </section>
-
-    </article>
-  </main>
+{{ define "header" }}
+  <header>
+    <hgroup>
+      <h1>{{ .Site.Title }}</h1>
+      <p>{{ .Site.Params.description | default "An agent-first approach to web generation." }}</p>
+    </hgroup>
+  </header>
+{{ end }}
+
+{{ define "content" }}
+  <article role="main">
+    <section>
+      <h2>Recent</h2>
+      {{ range first 10 .Site.RegularPages }}
+      <article>
+        <header>
+          <h3><a href="{{ .Permalink }}">{{ .Title }}</a></h3>
+          <p data-text="dim">
+            <time datetime="{{ .Date.Format "2006-01-02" }}">{{ .Date.Format "January 2006" }}</time>
+            {{ with .Params.eyebrow }} · {{ . }}{{ end }}
+          </p>
+        </header>
+        {{ with .Summary }}<p>{{ . }}</p>{{ end }}
+      </article>
+      {{ end }}
+    </section>
+  </article>
 {{ end }}