- Detect API-level errors (quota exceeded, invalid URL) in response JSON and store in scan_error instead of silently writing zeros - Show scan error message on the performance card when present - Show "No performance data — configure PAGESPEED_API_KEY" when all scores are 0 and no error was recorded - Add accessibility and best practices scores to performance card Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>