feat: add configurable image input preprocessing (#2028)

examples/cli/README.md

@@ -14,6 +14,12 @@ equivalent to `--log-level verbose`. If repeated, the last logging option wins.
 For direct image repair or automatic post-generation YOLOv8 detection followed by cropped inpainting, see
 [ADetailer](../../docs/adetailer.md).
 
+Use repeatable `--image-preprocess` rules to select resizing, cropping, padding,
+and resampling separately for each image input. Add `canny=true` to any input
+rule for edge detection. See
+[Image preprocessing](../../docs/image_preprocessing.md) for input selectors,
+input defaults, downstream model processing, mask alignment, and examples.
+
 Metadata mode inspects PNG/JPEG container metadata without loading any model:
 
 ```bash