Add negative_prompt STRING input. Priority chain for negative output:
1. negative_conditioning (pre-encoded CONDITIONING) - pass through as-is
2. negative_prompt (text) encoded via CLIP - removes need for external CLIPTextEncode
3. Popup default negative_prompt field in Refiner tab
4. Empty list if nothing is provided
Negative prompt field added to Refiner tab in popup with override toggle.
Override system extended with negative_prompt key.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>