Chord ties must compare pitch SETS, not authored array order

A tied chord requires every notehead of the first chord to have an identical-pitch counterpart in the second chord; the order pitches were listed in when authored is not musically meaningful.

Gould extends the same-pitch rule per notehead for chord ties ('each note of the chord is tied separately'); nothing in engraving practice attaches meaning to authoring order, only to sounding pitch content.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.