Trust rendered SVG bounds, not control points

Computing the bounding box from coordinates in path d= attributes was off by ~1.2% vertically vs the actually-rendered shape, because cubic bezier curves can dip past their control polygon. Rendering the SVG to PNG with macOS qlmanage -t -s 512 (no install needed) and measuring non-white pixels gave true rendered bounds, exposing the asymmetry. One transform nudge fixed it.