Chapter 61: The Computational Bi-Square

The bi-square of Book I (I.T41) has appeared at three enrichment levels: algebraic (E₀), topological (E₀ → E₁), and enriched (E₁+). This chapter constructs the fourth and final bi-square—the computational bi-square at E₂—and proves the τ-Admissibility Collapse: τ-P_adm = τ-NP_adm. The proof assembles constant-width Cook–Levin tableaux (Ch 55), polynomial CRT refinement (Ch 57), and the Product-Meet Collapse—the E₂ identity between searching for a witness (∧) and constructing the composite (×).