feat: add license files for JavaScript assets and implement DocItem component

- Added LICENSE.txt file for JavaScript assets in the build directory, including licenses for NProgress and React libraries.
- Introduced a new runtime JavaScript file for handling module loading.
- Created a new DocItem component to manage document rendering and metadata handling in the Docusaurus theme.
- Implemented tests for the docs proxy server to ensure proper routing to the configured docsPort.

ccw/docs-site/src/theme/DocItem/index.tsx

@@ -0,0 +1,46 @@
+import React, {type ReactNode} from 'react';
+import {HtmlClassNameProvider} from '@docusaurus/theme-common';
+import {useLocation} from '@docusaurus/router';
+import {DocProvider} from '@docusaurus/plugin-content-docs/client';
+import DocItemMetadata from '@theme/DocItem/Metadata';
+import DocItemLayout from '@theme/DocItem/Layout';
+import NotFoundContent from '@theme/NotFound/Content';
+import type {Props} from '@theme/DocItem';
+
+export default function DocItem(props: Props): ReactNode {
+  const location = useLocation();
+
+  // Docusaurus expects `content` to be a MDX component function with a
+  // `metadata` property attached. Under certain dev/proxy edge cases, this can
+  // be missing and the default theme crashes with:
+  // "Cannot read properties of undefined (reading 'id')".
+  const content = (props as unknown as {content?: unknown}).content as
+    | {metadata?: {id?: string}}
+    | undefined;
+
+  const docId = content?.metadata?.id;
+  if (!docId) {
+    if (process.env.NODE_ENV !== 'production') {
+      // eslint-disable-next-line no-console
+      console.error('[DocItem] Missing doc metadata', {
+        pathname: location.pathname,
+      });
+    }
+    return <NotFoundContent />;
+  }
+
+  const docHtmlClassName = `docs-doc-id-${docId}`;
+  const MDXComponent = props.content;
+
+  return (
+    <DocProvider content={props.content}>
+      <HtmlClassNameProvider className={docHtmlClassName}>
+        <DocItemMetadata />
+        <DocItemLayout>
+          <MDXComponent />
+        </DocItemLayout>
+      </HtmlClassNameProvider>
+    </DocProvider>
+  );
+}
+