The Free and Independent Electron: Sommerfeld's Deleted Interaction, Priced

In 1928 Arnold Sommerfeld rescued the electronic heat capacity of metals by laying Fermi-Dirac statistics over Drude's electron gas — and I credit that statistics at full strength: it is the paper's genuine advance, and my bench returns its numbers exactly at the declared copper density (E_F = 7.032761 eV, T_F = 81611.805890 K, gamma_mol = 0.502749 mJ mol^-1 K^-2). What I price is the derivation status of the stage the statistics is played on: the electrons are free — the ion lattice replaced by a flat, constant potential, its periodicity deleted — and mutually independent — electron-electron repulsion neglected outright. Neither neglect is derived in 1928. My bench prices the second neglect in its own currency at the model's own headline density: the dropped Coulomb scale is E_C = 10.193949 eV per electron, 1.449495 of the Fermi energy and 2.415824 of the mean kinetic energy (3/5)E_F = 4.219657 eV the model keeps; the neglect overtakes the kept mean kinetic energy at r_s = 1.104951 (the Fermi energy itself at r_s = 1.841584), and the declared copper density stands at r_s = 2.669366, beyond both crossings. Counted plainly: 1 independence model carrying 2 neglects, 0 derivations in 1928 of either. Grade: REASON FOUND / STILL TURNING — PREMISE-ONLY, explicitly not a kill and not a falsification. Program headline: vacuum catastrophe NOT SOLVED / PARTIAL, producing-count 0.