Paper FP-0: What survives an audit of Four-Sector Cosmology: a claims ledger, five tests, and the falsifiable core

Abstract Four-Sector Cosmology (FSC) is a series of self-published preprints that describe the universe as four sectors related by a Z4 rotation of time, t -> it, and that quote several numerical results as derived from this structure. This first draft audits the series. It does not propose a new model. Because FSC contains LCDM (Sector I alone reproduces it), a fit to present data cannot favour FSC; the question is what FSC forbids. We (1) trace each printed number in the papers we read to its source and classify it as derived, input, circular or inconsistent (audit items A1-A15); (2) test concrete realisations of the series against Planck and DESI DR2 data at the background level; and (3) state what remains, with explicit kill criteria. Findings. The composition 5:27:68, the Sector-IV decay constant, the symmetry-breaking parameter and the dark-fluid mass are inputs or rest on circular steps. In the realisations examined, a Sector-IV decay into matter with the parameters of Paper D is excluded by the CMB acoustic angle together with DESI DR2 BAO (Delta chi^2 = +2601, H0 = 48.5) and lowers H0; a w_IV = -1 decay is only weakly disfavoured. The phase mode of the CQ-C Sector-II field cannot carry the dark-matter energy density (56 orders of magnitude short) or form structure. The symmetry-breaking trigger leaves 1+w0 of order 1e-4 to 1e-3 for the displacement used in CQ-XI. A coupling of baryons to dark energy would multiply the baryon density by 3 to 9 for a DESI-like 1+w0. What remains is a short list of statements that LCDM also makes (w = -1, antimatter falls as matter, gravity-only dark matter) and one untestable relation (a 5.03 GeV dark-matter mass). The tests cover the realisations examined, not every possible FSC. The audit was made by the author of the series with the help of an AI system (Claude, Anthropic) and reviewed by an AI reviewer that executed no code and opened no primary sources; the scripts that produce every number are included (fp0_scripts.zip, with README.md).