Minor UI fixes

- article internal border overlap with folded-out details
- article type border-radius when there is only one article type selectable

app/assets/stylesheets/zammad.scss

@@ -4406,6 +4406,7 @@ footer {
   .article-content {
     color: hsl(60,1%,34%);
     position: relative;
+    z-index: 1;
     padding: 0 55px;
   }
 
@@ -4751,6 +4752,10 @@ footer {
     border-radius: 0 4px 4px 0;
   }
 
+  .pop-selectable:only-child {
+    border-radius: 4px;
+  }
+
   .pop-selectable-icon {
     fill: hsl(231,3%,40%);
   }