Detector response on circular worldlines in de Sitter spacetime: a sharp negative result for a single-temperature origin of the MOND acceleration scale

PAPER 1 — 10.5281/zenodo.21609173 Paper 1 of the Circular Vacuum Program, a preregistered computational study of quantum detector response on bound worldlines. We compute the response of Unruh-DeWitt detectors on circular orbits in de Sitter spacetime and confront a registered hypothesis: that the MOND acceleration scale a0 marks a single-temperature thermal threshold of the orbital vacuum. The result is a sharp negative. The detector-response merger is set by the orbital frequency scale, with deep-probe crossings roughly 36x below a0; a registered E = a law fails at face value by a factor ~912, with the corrected law frozen and independently verified; and the detailed-balance temperature is verified to equal H/2pi at every coupling tested, while the response itself is non-thermal. Every gate verdict, face-value miss, and correction ships in the sealed reproducibility capsule and the append-only figure addendum enclosed. FILES: paper PDF; LaTeX source with figures (zip); sealed reproducibility capsule (code, grids, frozen preregistrations, ledgers); append-only corrections/figure addendum. THE CIRCULAR VACUUM PROGRAM (7 papers): Circular worldlines in de Sitter — negative result on a single-temperature a0: doi:10.5281/zenodo.21609173 Eccentric orbits — the kinematic pedestal: doi:10.5281/zenodo.21609579 Exact EM/scalar identity, C_EM = 6 derived: doi:10.5281/zenodo.21609658 Vacuum dressing and exclusion bounds on modified inertia: doi:10.5281/zenodo.21609697 Laboratory contact — Sokolov-Ternov retrodiction: doi:10.5281/zenodo.21609721 Entanglement harvesting on bound dS worldlines: doi:10.5281/zenodo.21609752 Horizons against harvesting — dS, BTZ, Schwarzschild: doi:10.5281/zenodo.21609782 METHODS NOTE: The program operates under freeze-before-score preregistration with misses booked at face value, independent fresh-session construction and scoring, and multi-round adversarial review. Computations and drafting were performed with AI assistance (Claude, Anthropic), as acknowledged in each paper; all results are verified through the program's preregistration, hash-chained record, and independent-review discipline. This computes the thermometer, not the engine; the inertia coupling remains unsolved.