Stirling-PDF 是做什么的？
Analyse a branch or PR and automatically capture before/after screenshots of every UI surface its changes touch, then pixel-diff the pairs to surface what actually changed and assemble PR-ready before/after montage images. Generic and diff-driven: it derives the capture targets from the diff (changed tools/routes → URLs) instead of hand-listing screens, captures "before" from the base branch and "after" from the head, then keeps only the views that visually differ. Each comparison is auto-croppe