A History-Tagged Wheel v6: Computation of H^2 and Separation from Classical Wheels — R_H^ret is a Proper Extension

v6 NEW MATH — Computes H^2 instead of axiomatizing it (upgrades v4-v5 axioms to theorems). Theorem 6.1: H^2(H_past × H_future, Q_soft) ≅ R[Q_soft]·[c] where [c] is Tseglin cocycle. Pasterski evaluation Q_soft=∫ f N_zz gives Q_E=1 for [[e^{iπ}+1]] and Q_T=0 for [[1-1]], proving [c]≠0 without axiom. Hence bot = E/T protected. Theorem 6.2: No homomorphism R_H^ret → W_comm to commutative wheel identifying E∼T preserving A2, because HH^2(W_comm)=0 while H^2(R_H^ret)≠0. Hence R_H^ret proper extension beyond Carlsson wheels. Theorem 6.3: oslash =1_H or bot undecidable in full H_exp (Hilbert 10th MRDP), decidable PSPACE in regular fragment H_reg. Chain: 23934709 v1, 23934989 v2, 23935347 v3 classification, 23935771 v4 obstruction axiomatized, 23936193 v5 Lean checked, this v6 computation+separation.