Theorem: delta R_star^2 - R_p^2 = 0 (transit-depth disk-area-ratio identity)

Theorem (transit-depth-ratio canonical): delta = (R_p / R_star)^2 rearranges to delta R_star^2 = R_p^2, so the residual delta R_star^2 - R_p^2 = 0 vanishes identically. Canonical sympy pins: delta_d, R_star, R_p = sp.symbols('delta_d…