fix: rewrite markdown doc requests internally instead of 303 redirect (#808)

Agents requesting docs with Accept: text/markdown were getting 303
redirects to .md URLs, which many HTTP clients don't follow properly.
Instead of redirecting, internally rewrite the request to the .md route
and serve the markdown content directly.

https://claude.ai/code/session_01VBx5hnhWturAn1bBo68sCt

Co-authored-by: Claude <noreply@anthropic.com>

Author: tannerlinsley

src/server.ts

@@ -28,13 +28,14 @@ export default createServerEntry(
             url.pathname.includes('/docs/') &&
             !url.pathname.endsWith('.md')
           ) {
-            logRequestEnd(context, 303, { redirectToMarkdown: true })
-            return new Response(null, {
-              status: 303,
-              headers: {
-                Location: `${url.pathname}.md`,
-              },
+            const mdUrl = new URL(request.url)
+            mdUrl.pathname = `${url.pathname}.md`
+            const mdRequest = new Request(mdUrl, request)
+            const mdResponse = await handler.fetch(mdRequest)
+            logRequestEnd(context, mdResponse.status, {
+              rewrittenToMarkdown: true,
             })
+            return mdResponse
           }
 
           const response = await handler.fetch(request)