chore: import upstream snapshot with attribution

docs/src/theme/CodeBlock/ContentHeader/index.tsx

@@ -0,0 +1,20 @@
+import React, { type ReactNode } from 'react';
+import clsx from 'clsx';
+import Buttons from '@theme/CodeBlock/Buttons';
+import styles from './styles.module.css';
+
+export interface ContentHeaderProps {
+  language?: string;
+}
+
+export default function ContentHeader({ language }: ContentHeaderProps): ReactNode {
+  return (
+    <div
+      className={clsx(styles.codeBlockHeader)}
+      aria-label={`Code block header for ${language} code with copy and toggle buttons`}
+    >
+      <span className={styles.languageLabel}>{language}</span>
+      <Buttons />
+    </div>
+  );
+}

docs/src/theme/CodeBlock/ContentHeader/styles.module.css

@@ -0,0 +1,16 @@
+.codeBlockHeader {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  padding: 0.25rem 0.5rem;
+  background: var(--prism-background-color);
+  position: sticky;
+  top: var(--ifm-navbar-height, 3.125rem); /* Stick below the Docusaurus navbar; fallback for safety */
+}
+
+.languageLabel {
+  font-size: 0.75rem;
+  font-weight: 600;
+  color: var(--ifm-color-emphasis-600);
+  padding: 0.3125rem;
+}