DENS — the Density–ENergy of Space: the galactic acceleration scale a₀ = A√ρ as a reading of the vacuum energy density, from SPARC rotation curves to the measured a₀(z)

The MOND acceleration scale a₀ is read not as a universal constant but as a direct observable of the local medium: a₀ = A√ρ, the energy density of the vacuum at a given place (the DENS framework). Two results meet real data under one identical pipeline. (1) The radial-acceleration relation of 153 SPARC galaxies (3166 points) is reproduced by a fixed-shape law, g_obs = √(g_bar² + g_bar·a₀), at a maximum-likelihood intrinsic scatter (0.046 dex) similar to the fitted MOND simple-ν comparator’s (0.045 dex); a₀ = 1.39 ± 0.03 (fixed shape) and 1.13 ± 0.03 ×10⁻¹⁰ m s⁻² (MOND) on the same data. Both laws carry one free parameter; the distinction is provenance — the fixed shape is motivated by the substrate decomposition rather than selected from a family of interpolation functions. (2) The first measured redshift evolution of a₀ (MUSE-DARK III) is read, through a₀ = A√ρ, as a density profile of each place. The weak-field limit recovers the classical tests via an isotropic exponential (Yilmaz-type) metric, 1PN-degenerate with Schwarzschild. This record contains the paper and a reproducibility package (staged SPARC fit scripts, Solar-System geodesic integrators, figure script, captured outputs). The computations were independently reproduced by an independent AI co-scientist re-implementation (not human peer review): this establishes computational reproducibility of the numbers, not validation of the physical interpretation.