Chapter 2: Importing Book~III: The E₁ Template

Books I through III built the mathematical kernel of Category τ: a five-generator categorical structure (Book I), a holomorphic fibration with spectral boundary (Book II), and a complete first enrichment layer whose sector couplings are rational functions of a single constant (Book III). This chapter collects the three principal deliverables that Book IV inherits. Nothing is re-derived; every result is cited by registry label and used as a black-box contract.