Turn placement (over the note vs. inserted after it) is not authorable

A turn can sit directly over a notehead (ornamenting that note itself) or be placed in the space AFTER a note, between it and the next, indicating the turn's figure is inserted between the two written pitches — a real distinction with different rhythmic execution, common in Classical-era ornamentation.

A lesson intends to teach the "turn between two notes" Classical convention, but `ornament: 'turn'` (both Model A and Model C) has no placement parameter — the glyph always renders directly over the notehead's stem side, never in the inter-note gap.

Gould, Behind Bars, ch. Ornaments, distinguishes over-the-note vs. after-the-note turn placement explicitly with different notated positions.

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