L1 Paper 3 Fermion Yukawa Mass Equivalence

This paper establishes the equivalence between fermion mass assignments and Yukawa coupling structure within an admissible local skin. The analysis is eliminative: it shows that once admissibility, standing preservation, and identity persistence are fixed, fermion masses cannot be treated as independent structural inputs distinct from Yukawa relations. Mass is classified as a representational consequence of admissible coupling rather than as a primitive or freely specifiable parameter. Attempts to vary fermion masses independently of Yukawa structure are shown to either violate equivalence closure, collapse identity under composition, or introduce illicit scope transport between descriptive layers. The paper introduces no new primitives and provides no mechanisms or calculational prescriptions. Its contribution is boundary-setting: it clarifies why fermion masses and Yukawa couplings are structurally equivalent within standing-preserving bookkeeping, and why treating them as separable degrees of freedom is inadmissible rather than merely phenomenologically disfavored.