Only include an <hgroup> in the page summary if there's a description to include

Otherwise just use an <h2>. Add .page-summary__heading to both elements and update
the styles.

assets/css/099_page_summary.css

@@ -18,11 +18,11 @@
     margin-block-end: var(--space-xl);
   }
 
-  > hgroup {
-    line-height: 1;
+  .page-summary__heading {
     margin-block: 0 var(--space-xs);
 
     h2 {
+      line-height: 1;
       font-size: var(--text-l);
       margin-block: 0;
     }

layouts/_default/page_summary.html

@@ -1,18 +1,23 @@
 <article class="page-summary">
-  <hgroup>
-    <h2><a href="{{ .Permalink }}">{{ .LinkTitle | markdownify }}</a></h2>
-    {{ if and (.Params.rendersSummary | default true) -}}
+  {{ if and (.Params.rendersSummary | default true) (gt (len .Description) 0) -}}
+    <hgroup class="page-summary__heading">
+      <h2><a href="{{ .Permalink }}">{{ .LinkTitle | markdownify }}</a></h2>
       {{ with .Description }}
         <p>{{ . | markdownify }}</p>
       {{ end }}
-    {{ end }}
-  </hgroup>
+    </hgroup>
+  {{ else }}
+    <h2 class="page-summary__heading"><a href="{{ .Permalink }}">{{ .LinkTitle | markdownify }}</a></h2>
+  {{ end }}
+
   {{- if .Date -}}
     {{- partial "page/date.html" (dict "page" .) -}}
   {{- end }}
-  {{- if ne hugo.Environment "production" -}}
+
+  {{- if not hugo.IsProduction -}}
     {{ partial "page/taxonomy_draft.html" (dict "page" .) }}
   {{- end -}}
+
   {{ partial "page/taxonomy_list.html" (dict "page" . "taxonomy" "categories") }}
   {{ partial "page/taxonomy_list.html" (dict "page" . "taxonomy" "tags") }}
 </article>