Fix comma insertion logic to prevent undefined entries

Improvements:
- Check for existing trailing comma before adding separator
- Validate generated entry contains required fields
- Prevents duplicate commas when inserting multiple claims sequentially

This fixes the "Type 'undefined' is not assignable" error

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/add-claim-to-data.ts

@@ -96,13 +96,21 @@ export function addClaimToDataFile(claim: NewClaimInput): void {
   // Generate new entry
   const newEntry = generateClaimEntry(claim);
 
+  // Validate the generated entry contains required fields
+  if (!newEntry.includes('slug:') || !newEntry.includes('title:') || !newEntry.includes('claims:')) {
+    throw new Error('Generated entry is missing required fields');
+  }
+
   // Insert before the closing bracket
   const insertPosition = match.index;
   const before = fileContent.substring(0, insertPosition);
   const after = fileContent.substring(insertPosition);
 
-  // Add comma after last entry if needed
-  const newContent = before.trimEnd() + ',\n' + newEntry + after;
+  // Add comma after last entry if needed (check if there's already a trailing comma)
+  const trimmedBefore = before.trimEnd();
+  const needsComma = !trimmedBefore.endsWith(',') && !trimmedBefore.endsWith('[');
+  const separator = needsComma ? ',\n' : '\n';
+  const newContent = trimmedBefore + separator + newEntry + after;
 
   // Write back to file
   fs.writeFileSync(claimsFilePath, newContent, 'utf-8');