style(storybook): refine foundation and navigation stories

src/components/menubar.stories.tsx

@@ -97,10 +97,10 @@ export const All: Story = {
   render: () => (
     <StoryPage>
       <StoryPageHeader title="Menubar" />
-      <StorySection title="Overview">
-        <div style={{ minHeight: 384 }}>
-          <Specimen />
-        </div>
+      {/* The section is titled Basic (was Overview). The former `minHeight: 384` reserved room for the open menus; they render in a
+          portal over the page (with collision handling), nothing follows this section, so the fixed height is not needed. */}
+      <StorySection title="Basic">
+        <Specimen />
       </StorySection>
     </StoryPage>
   ),