Fix check-links workflow: exclude malformed ToC URLs and truncate PR body

Co-Authored-By: David Konigsberg <davidakonigsberg@gmail.com>

Author: devin-ai-integration[bot]

.github/workflows/check-links.yml

@@ -35,6 +35,7 @@ jobs:
             # Malformed ToC anchor links generated by the docs platform
             # These contain internal routing params (domain/host/auth/audience/version/path)
             # and are not real broken links — this is a fern-platform rendering bug
+            "buildwithfern\\.com/_/buildwithfern\\.com/",
             "app\\.buildwithfern\\.com/buildwithfern\\.com/",
             
             # Placeholder/example URLs
@@ -508,7 +509,7 @@ jobs:
             status=$(echo "$line" | sed -E 's/.*\[([0-9]+)\].*/\1/')
             
             # Skip malformed ToC anchor links (fern-platform rendering bug)
-            if echo "$url" | grep -qF 'app.buildwithfern.com/buildwithfern.com/'; then
+            if echo "$url" | grep -qE 'buildwithfern\.com/_/buildwithfern\.com/|app\.buildwithfern\.com/buildwithfern\.com/'; then
               continue
             fi
             
@@ -824,6 +825,15 @@ jobs:
             scaffoldContent += '\n---\n';
             scaffoldContent += `[View workflow run](https://github.com/${owner}/${repo}/actions/runs/${context.runId})\n`;
 
+            // Truncate PR body to stay under GitHub's 65536 character limit
+            // The full content is still written to the scaffold file
+            const MAX_PR_BODY_LENGTH = 60000; // leave headroom for safety
+            let prBody = scaffoldContent;
+            if (prBody.length > MAX_PR_BODY_LENGTH) {
+              const truncationNote = `\n\n---\n⚠️ **Report truncated** — full list is in the scaffold file (\`${filePath}\`) on the branch.\n[View workflow run](https://github.com/${owner}/${repo}/actions/runs/${context.runId})\n`;
+              prBody = prBody.substring(0, MAX_PR_BODY_LENGTH - truncationNote.length) + truncationNote;
+            }
+
             // Get the base branch ref
             const baseRef = await github.rest.git.getRef({
               owner,
@@ -961,7 +971,7 @@ jobs:
                 title: 'Fix broken links (Devin)',
                 head: branchName,
                 base: baseBranch,
-                body: scaffoldContent,
+                body: prBody,
                 draft: true,
               });