When the first pair candidate places more parts than needed (e.g., 17
when target is 10), sort by BoundingBox.Top, trim from the top until
exactly targetCount remain, and use that Top as the new work area
height. All subsequent candidates fill this smaller area, dramatically
reducing fill time.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>