Cone Diameter Growth and the Mixing-Boundary Obstruction for Twisted Bird–Map Operators (Paper 41 in the Non-Holomorphic Fractal Series)

Paper 41 in the Non-Holomorphic Fractal Series. Paper 40 established positive BV cones for twisted Bird-map transfer operators on the central window I_core = [0.84, 0.90] and proved uniform Hilbert projective diameter bounds there, together with a conditional projective contraction theorem and a qualitative boundary obstruction on the enlarged rigidity interval I_rig = [0.70, 1.10]. In this paper we convert that obstruction into a numerical and geometric diagnostic for cone diameter and invariant-density oscillation near the mixing boundary, using only the existing certified grid and transfer-operator infrastructure. We define a projective-diameter proxy D(h, ε) and an invariant-density oscillation functional…