fix: validate empty CSV column names and improve mismatch error messages (#1010)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: bot_apk <apk@cognition.ai>
Co-authored-by: Alfredo Garcia <alfredo.garcia@hallmark.edu>
Co-authored-by: Zane Hyatt <zane.hyatt@airbyte.io>