Add news posts with banner summaries on the home page

Posts live in content/post/; the five latest are summarised on the home
page. Builds for check/deploy go to build/ so they do not collide with a
running hugo server writing to public/.

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

layouts/home.html

@@ -1,14 +1,25 @@
 {{ define "main" }}
 <h1>{{ .Title }}</h1>
 <div class="content">{{ .Content }}</div>
+{{ with site.GetPage "/post" }}
+{{ $posts := .RegularPages.ByDate.Reverse }}
+{{ if $posts }}
+<h2>{{ .Title }}</h2>
+<div class="posts">
+  {{ range first 5 $posts }}{{ partial "post-summary.html" . }}{{ end }}
+</div>
+{{ if gt (len $posts) 5 }}<p><a href="{{ .RelPermalink }}">All posts →</a></p>{{ end }}
+{{ end }}
+{{ end }}
+<h2>Sections</h2>
 <div class="cards">
   {{ range site.Menus.main }}
-  {{ with .Page }}
+  {{ with .Page }}{{ if ne .Section "post" }}
   <a class="card" href="{{ .RelPermalink }}">
     <strong>{{ .Title }}</strong>
     <span>{{ len .RegularPages }} {{ if eq (len .RegularPages) 1 }}page{{ else }}pages{{ end }}</span>
   </a>
-  {{ end }}
+  {{ end }}{{ end }}
   {{ end }}
 </div>
 <h2>Browse the museum</h2>