Traced contours now end with a closing Z

Contours in a trace already ended where they started, but most didn't say so: 453,042 of the 598,639 we counted had no closing Z. Software that goes by that command can read such a contour as an open line, which a laser can score but not cut out. Every contour in a new SVG trace now ends with Z, and the trace looks the same.

A file traced before 28 October stays as it is. To close it, trace the image again or close its paths in your editor.