fix(docs): replace broken page copy buttons with working single button

The three page-level buttons (Copy MD, View MD, Copy MDX) were broken
because the fetch URL missed the /ktx basePath. Replace with a single
"Copy as Markdown" button that strips frontmatter from the MDX source
already available client-side — no fetch needed. Drop the .md link
since agents discover markdown URLs through llms.txt and content
negotiation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs-site/app/docs/[[...slug]]/page.tsx

@@ -51,10 +51,7 @@ export default async function Page(props: {
         <>
           <div className="flex flex-col gap-3 sm:flex-row sm:items-start sm:justify-between sm:gap-4">
             <DocsTitle>{page.data.title}</DocsTitle>
-            <DocsPageActions
-              markdownUrl={`${page.url}.md`}
-              mdxSource={mdxSource}
-            />
+            <DocsPageActions mdxSource={mdxSource} />
           </div>
           <DocsDescription className="wrap-anywhere">
             {page.data.description}