Artian Radiative Lorentz-Stability: Exact Collins Response, Euclidean-First Unitarity, and the Postulate E Boundary

Artian Radiative Lorentz-Stability The paper tests both the QTT null and whether the calculation is capable of seeing the forbidden deformation: \[ \Pi_{\rm SME}^{\rm LV}\!\left[\Gamma_{1\rm PI}^{\rm Artian}-\Gamma_{1\rm PI}^{\rm Lorentz}\right]_{d\leq4}=0,\qquad \left.\frac{d\Delta c}{d\xi}\right|_{\xi=1}=\frac{\alpha}{12\pi}\neq0. \] The first equation says the dangerous dimension-three and dimension-four Lorentz-violating operators vanish in the executed local electron-photon one-loop sector. The second proves that the same loop packet responds at first order when the regulator is deliberately made anisotropic. The null is therefore a symmetry zero, not an insensitive calculation. Scientific result: a QTT zero-fit source-explanatory victory for radiative Lorentz stability in the executed sector. No observed SME coefficient, preferred-frame counterterm, compensating cancellation, or low-energy Lorentz-restoring fit is used to obtain the zero. Ward identities, SME projection, Euclidean loop tools, and Cutkosky continuation retain standard ownership. The completed-cell scalar regulator and simultaneous zero/negative-control pair are QTT-native. Wider Standard Model, gravity-loop, and nonlocal completion questions remain separately scoped.