The degree-two Ext calculation for a covariant coherent defect

noncomputable def MagnitudeConjecture.RightModule.FiniteIndecomposableSkeleton.finiteCovariantDefectPresentationLinearEquiv {k A : Type u} [Field k] [IsAlgClosed k] [Ring A] [Algebra k A] [FiniteDimensional k A] [IsNoetherianRing Aᵐᵒᵖ] (S : FiniteIndecomposableSkeleton k A) [CategoryTheory.HasExt S.FiniteCovariantFunctor] {K : CategoryTheory.ShortComplex FG} (hK : K.ShortExact) (X : S.IndecCategoryᵒᵖ) : (((S.finiteCovariantDefectLeftShortComplex K).X₁ ⟶ S.finiteCovariantRepresentableOnSkeleton.obj X) ⧸ ProjectivePresentationExt.presentationRange (S.finiteCovariantDefectLeftShortComplex K) (S.finiteCovariantRepresentableOnSkeleton.obj X)) ≃ₗ[k] CategoryTheory.Abelian.Ext (S.finiteCovariantDefect K) (S.finiteCovariantRepresentableOnSkeleton.obj X) 2

The two short exact halves compute reverse coherent duality as the quotient attached to the left covariant-representable presentation.