f1c5af5's set head (an image's name up to its first number) split sets whose images aren't named alike: "a1.jpg" beside "a1 (2).jpg", and "468_1000.jpg" whose first number is the image's (1 release became 211 and 161 on the corpus). The random volume stem stays. Tests keep both sets whole. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>