Short theme codes carry hidden and reordered layers

A style with a layer group hidden used to fall back to a 118-character ut1. document. The short code now packs the seven visibility switches and the draw order into a few extra characters: a style is u00 and up, a named preset is three characters, and a style with a group hidden is six.

• Codes printed before today no longer decode: re-export from unmap.dev/create, or reinstall map-themes for the new preset codes
• ut1. is now only for hand-edited colours; everything simple mode and the layers panel can produce is a short code

Action requiredCodes printed before this change no longer decode. Re-export from unmap.dev/create, or reinstall map-themes, before you rely on a saved code.