Shear-Overshoot Obstruction to Smooth Daughter-Universes in a Nonpolynomial Regular-Black-Hole Completion

This preprint studies whether a reduced black-hole-to-daughter-universe bounce can be realized as a smooth finite-thickness canonical transition in a four-dimensional nonpolynomial regular-black-hole completion. The main result is a profile-independent shear-overshoot theorem for smooth spherical matching. If a candidate wall satisfies a genuine angular turning condition and joins the finite exact parent, exact radial-tangent transport requires the wall shear to become positive somewhere and subsequently reverse sign before matching the negative-shear parent. For the fixed spatial geometry considered here, this yields the quantitative necessary bound ||Delta_+||_infinity >= 3.66002. A stronger completion-specific result is then established. Under fixed ADM mass and radial gauge, exact-parent matching on a nonempty outer overlap, regularity-localized nonlinear unique continuation, normalized momentum uniqueness, and exact tangent transport exclude every admissible smooth spherical turning wall of the specified completion. Closed-FLRW finite-radius bounce and an open local Bianchi-IX bounce basin are included as consistency results rather than priority claims. The no-go theorem is deliberately limited to the stated constrained completion and matching architecture. It does not exclude alternative completions, nonspherical walls, noncompact matching constructions, or finite spin. The accompanying reproducibility package contains the archived numerical profile, proof-critical certificate scripts, Bianchi-IX numerical diagnostics, SHA-256 checksums, and instructions required to reproduce the computational checks.