IV.R43 — Donut Persistence

T² fibre survives from 1st to 2nd Edition. Shape ratio r/R = ι_τ still determines all physics. Donut now EARNED not assumed: Book I earns L algebraically, Book II earns T² from Central Theorem, Book III earns sectors as L-characters, Book IV earns particles as defect bundles. 1st Ed: donut as geometric intuition. 2nd Ed: donut as theorem.