Fix preprocessor_config.json: set do_resize=false, add patch_size/max_num_patches/return_row_col_info to match LiquidAI/LFM2-VL-450M. The auto-generated config from lfm2-vl-export caused double-resize, inflating input_ids from 285 to 653 and producing [] on all borderline detections.

v9-e3 ONNX export (8x D4 aug fine-tune, IoU 0.332)