feat(docs): add Stainless vs Fern comparison pages as hidden resources

- Add comprehensive comparison document (stainless-comparison-full.mdx)
- Add concise summary comparison (stainless-comparison-summary.mdx)
- Mark both pages as hidden in docs.yml navigation
- Pages accessible only via direct link for sales engineering use

Co-Authored-By: Chris McDonnell <[email protected]>

Author: devin-ai-integration[bot]

fern/products/docs/docs.yml

@@ -287,4 +287,15 @@ navigation:
         path: ./pages/developer-tools/vale.mdx  
       - page: View Markdown
         path: ./pages/developer-tools/view-markdown.mdx
+  - section: Resources
+    collapsed: true
+    contents:
+      - page: Stainless vs Fern comparison (full)
+        path: ./pages/resources/stainless-comparison-full.mdx
+        slug: resources/stainless-comparison-full
+        hidden: true
+      - page: Stainless vs Fern comparison (summary)
+        path: ./pages/resources/stainless-comparison-summary.mdx
+        slug: resources/stainless-comparison-summary
+        hidden: true