Tie direction for chords
Ties for chords (in a single-voice context) have a few simple rules:
* The highest tie in the chord should curve up
* The lowest tie in the chord should curve down
* The ties in the middle should curve up if they are above the middle line, or curve down if they are on/below the middle line
* For intervals of a second the ties should curve opposite directions if possible
In a multi-voice context MuseScore already behaves correctly:
* Ties should curve the same direction as the stems.
Attached is a full test suite with reference images of the expected behavior on the left side and actual MuseScore behavior on the right side.