Generated image is cropped when using smaller output size to reduce VRAM and processing time in Flux Kontext

Use `max_area` in FluxKontextPipeline, default `max_area=1024**2`. I set `max_area=768**2`, and output is cropped

Original image:


Output with `max_area=1024**2`:

Output with `max_area=768**2`:

Start with FluxKontextPipeline and reproduce the reported behavior using max_area=1024**2 and max_area=768**2. Compare the generated outputs with the original image and trace how the smaller max_area is applied; done means the reduced-size output is not unexpectedly cropped.

Written by the indexing model from the issue text.