Shortcuts: Move SectionHeader title below top line and refine styling (#18721)

packages/cli/src/ui/components/shared/SectionHeader.test.tsx

@@ -30,9 +30,15 @@ describe('<SectionHeader />', () => {
       title: 'Narrow Container',
       width: 25,
     },
-  ])('$description', async ({ title, width }) => {
+    {
+      description: 'renders correctly with a subtitle',
+      title: 'Shortcuts',
+      subtitle: ' See /help for more',
+      width: 40,
+    },
+  ])('$description', async ({ title, subtitle, width }) => {
     const { lastFrame, waitUntilReady, unmount } = renderWithProviders(
-      <SectionHeader title={title} />,
+      <SectionHeader title={title} subtitle={subtitle} />,
       { width },
     );
     await waitUntilReady();