Multiple accidentals within one chord must stagger further left when they would overlap each other

When a chord carries two or more accidentals close in pitch, the accidentals cannot sit in one vertical column — the lower one is pushed further left so the two glyph bounding boxes clear.

A tone-cluster chord [C4,C#4,D4] where the natural and sharp signs are drawn in the same horizontal column and overlap.

Gould, Behind Bars, ch. 'Accidentals — in chords', explicit diagrams of staggered accidental columns; Read, Music Notation covers the same convention. VexFlow's own `Accidental.format` (Category.Accidental, run third in ModifierContext.preFormat, after Dot and FretHandFinger) implements the stagger via `left_shift` accumulation.

This rule needs the notated content and the rendered result together — the score says what should happen, the page says whether it did.