CFG rescale and dynamic thresholding fix SDXL oversaturation at high guidance

Photoroom engineers found that classifier-free guidance above 7.5 on their fine-tuned SDXL pipeline caused oversaturated renders and clipped highlights. They applied CFG rescale at 0.7 and dynamic thresholding to restore image quality without retraining. The fixes address the variance inflation that occurs when guidance extrapolates beyond the model's training distribution.