- ErrorType enum with NETWORK, VALIDATION, SYSTEM, AUTH
- KBError base class with to_dict method for serialization
- NetworkError with status_code and auto-generated suggestion
- ValidationError with validation_errors list
- SystemError with system_message
- AuthError with auth_type
All errors include step_name, input_summary, error_type, message,
and suggestion for rich debugging context.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
