X72-40: Hardy-BMO Dual Commutator

Picks up Round 39's proof that incompressibility gives a Hardy compensation but no automatic Dini gain (STOP-C43), and switches to a dual route, requiring q∈ℋ^1 with dual commutator [u·∇,𝒯_0*]E_p∈BMO. Using Round 38's Pressure Self-Commutator Null Identity, it reduces the dual target to [D_u,𝒯_0*]C, involving only the local trace-free cofactor C_S^0, and proves that the Hardy side can be paid directly from the incompressible enstrophy — but the standard Coifman–Rochberg–Weiss L^p commutator estimate does not by itself deliver the required BMO target: the criticality of a full derivative still sits on the BMO side, with threshold s_u+s_C=1. STOP-C44 (Hardy-BMO Transfer/Two-Increment BMO Endpoint Gap) hands the problem to the next round, to look for extra cancellation from the cofactor's special algebraic structure.