Entropy-Response Gravity: a foundational derivation of Modified Newtonian Dynamics from horizon thermodynamics

Foundational paper (T1) of the Entropy-Response Gravity (Bipartite KMS Gravity) programme. The Bekenstein-Hawking entropy law S=A/(4G) at the bipartite Rindler-de Sitter horizon uniquely determines two of MOND's three parameters via two independent derivations: (i) the fluctuation-dissipation theorem on the local Rindler worldline, with the Pythagorean Narnhofer-Peter-Thirring temperature T_eff^2 = T_U^2 + T_GH^2, giving the standard interpolating function mu(x) = x/sqrt(1+x^2) (n=2) as the ratio of directed Unruh friction to total horizon friction; (ii) Jacobson's derivation of the Einstein equations at a local Rindler horizon in de Sitter space, giving F'(Q) = mu(sqrt(Q)) for the AeST kinetic function. Both yield a_0 = cH_0/sqrt(4 pi^2 - 1) from the matching r_R = lambda_T, with the structural decomposition (2 pi)^2 - 1. The gravitational coupling G remains external input, discussed transparently. Version 2: the interpolating-function label is corrected to the standard form (n=2) throughout; companion-paper journal-submission claims are removed (companions cited by Zenodo archive), while genuine third-party citations to papers published are retained. No physics content changed. Pre-registered at OSF 10.17605/OSF.IO/8Z27K and 10.17605/OSF.IO/5HCGF.