Improve drawing experience

Ideas to improve Fontra's drawing experience:
- cap-corners (but variable)
- cap-segment (but variable)
- being able to see all masters at once in a row, as well as any location of the design-space
- being able to see and locate interpolation errors at a glance
- edit contours and components order simply and quickly (like percolator)
- Hanzi database management with ability to import elements simply from one glyph to another ("Hanzi choose and pick")
- smooth junction of 2 contours even in curves and diagonals
- CJK-frame script-dependent
- extensions like speedpunk / RMX tools
- power-ruler always on
- automatic OT features (like 'vert' feature for JP)

The issue is a broad list of drawing-editor ideas and names no files, tests, or entry points. First determine which idea, if any, is in scope and locate the corresponding editor subsystem; completion criteria are not defined and would need to be agreed before implementation.

Written by the indexing model from the issue text.