IV.T165 — A = 1 - (3/2)*iota_tau^2 at -887 ppm from PDG 0.826 (tau-effective)

Tau-effective: Wolfenstein parameter A = 1 - (3/2)*iota_tau^2 = 0.82527 at -887.3 ppm from PDG A=0.826. Best formula found in systematic scan. Structural interpretation: A measures the deviation of the second-generation CKM mixing from unity; the (3/2) coefficient may relate to 3 force sectors times (1/2) from the lemniscate two-lobe structure. Wave 4B best was sqrt(1-iota_tau) at -17433 ppm; A = 1-(3/2)*iota_tau^2 improves by factor ~20. Also: A = 1-(13/8)*iota_tau^2 at -18516 ppm; 13/8 is CF-motivated (a_2=13), so 3/2 is structurally preferred.