Ring Geometry

The pure core of the ring figures: circle points with any node at twelve o'clock, shared-note labels pushed off each edge, arrows trimmed to node rims, the line-of-thirds strip's extent, and the ring roll's column placement (by chord or by beats, with a label gutter at each re-cut phrase), lane positions and cell paint by mark. Also the structural view model a ring roll is drawn from, so a theory library's roll object can be passed as is.