Merge upstream fumadocs dev (16.6.17) with @hanzo/docs namespace rename

Merge 131 upstream commits from fuma-nama/fumadocs dev branch, bringing
framework packages to v16.6.17. All fumadocs-* and @fumadocs/* package
references renamed to @hanzo/docs-* namespace.

Upstream additions:
- packages/content/ (@hanzo/docs-content) - Fuma Content adapter
- packages/epub/ (@hanzo/docs-epub) - EPUB export support
- MarkdownCopyButton, ViewOptionsPopover in docs page layout
- Flexsearch, Orama search integration
- Shiki v4 upgrade
- Various UI framework improvements

Hanzo customizations preserved:
- apps/docs/content/ (all Hanzo service/project docs)
- apps/docs/app/ (Hanzo homepage, AI chat, subdomain routing)
- apps/docs/components/ (AI search, error boundaries, auth)
- apps/docs/lib/ (source config, OpenAPI, metadata)
- Webpack alias layer for upstream project doc imports
- MdxErrorBoundary wrapper for graceful MDX failures

examples/python/components/mdx.tsx

@@ -0,0 +1,11 @@
+import defaultMdxComponents from '@hanzo/docs/ui/mdx';
+import type { MDXComponents } from 'mdx/types';
+import * as Python from '@hanzo/docs/python/components';
+
+export function getMDXComponents(components?: MDXComponents) {
+  return {
+    ...defaultMdxComponents,
+    ...Python,
+    ...components,
+  } satisfies MDXComponents;
+}