Add broken links scaffold for Devin to fix

Author: github-actions[bot]

.github/broken-links/broken-links.md

@@ -0,0 +1,25 @@
+@devin-ai-integration Please fix the broken links detected by the scheduled link checker.
+
+**Instructions:**
+1. For each URL listed below, identify the source file containing the broken link
+2. Try to find the correct replacement URL. Common fixes include:
+   - Updating outdated commit SHAs to the latest commit
+   - Fixing URL-encoded paths
+   - Updating renamed file paths
+3. **IMPORTANT: If you cannot confidently find a correct replacement** (e.g., the only signal is a 5xx/503 error, connection reset, or rate limiting), **do NOT remove or modify the link**. Instead, leave it unchanged and add a PR comment on the relevant line asking for manual validation.
+4. Only update links/paths contained in this PR, not other links that follow a similar pattern
+5. Run `fern docs dev` locally to verify your changes don't break anything
+6. Push your fix to this PR branch
+7. After CI posts a preview link, use it to verify that your changes actually fix the underlying issue, then post a comment to the PR mentioning that you have tested it using the preview link
+8. When the PR is ready for review, request a review from @davidkonigsberg in GitHub and send a message in the Devin session that includes "<!here>" to alert everyone in the channel. 
+9. Delete the scaffold file (.github/broken-links/broken-links.md) as part of your fix
+
+**Broken Links:**
+
+
+## Non-429 Broken Links
+
+- [404] https://buildwithfern.com/products/sdks/custom-code.mdx
+
+---
+[View workflow run](https://github.com/fern-api/docs/actions/runs/25435650842)