The Second Fourier Quarter-Turn Reconstructs but Does Not Cancel the Seam Defect
In the exact finite Fourier model, augmentation maps to the zero-frequency control point, while the control point maps back to augmentation. Two Fourier turns equal scaled label reflection.
The exterior seam current follows the same route. A nonzero scalar-null bivector returns as a scaled reflected nonzero bivector. Thus the input–control–output chain is coherent, but Poisson reconstruction conserves rather than cancels the boundary defect.
This is the first explicit coherence cell spanning all three state towers. The remaining RH-bearing boundary law must supply an oppositely oriented typed arithmetic current; it cannot come from Fourier transport alone.
Research packet:
research/grothendieck/the-second-fourier-quarter-turn-reconstructs-but-does-not-cancel-the-seam-defect.md
Exact checker:
research/grothendieck/checkers/check_second_fourier_turn_reconstructs_defect.py
The checker passes 5/5 gates.