Module cip_priority 

v0.1.93: Full multi-sphere CIP (Cahn–Ingold–Prelog) priority comparison.

Implements hierarchical digraph CIP rules with BFS sphere expansion, phantom atoms for double bonds, and atomic mass tiebreaking. This replaces the simplified 1-sphere CIP in stereo2d.rs / stereo3d.rs.

Functions

compare_branches

Compare two branches from center starting at a and b.