Comprehensive Experimental Test Regime for Probing Vacuum Mode Structure at the Fundamental Casimir Cavity Cutoff

We present a comprehensive, phased experimental test regime for the CASIMIR-CUTOFF program, which investigates the optical properties of a transparent Casimir cavity in the unexplored wavelength-matched regime 2d, where the probe photon wavelength equals twice the plate separation. The test regime spans six phases---from proof-of-concept validation through baseline Fabry-P\'erot characterization, cutoff anomaly search, signal verification, advanced measurements incorporating quasicrystalline boundary conditions, and contingent thrust characterization. Each phase specifies detailed measurement procedures, equipment configurations, acceptance criteria, statistical thresholds, and go/no-go decision gates. Novel elements include the use of Fibonacci gratings and Penrose tilings as plate surface patterns to impose aperiodic boundary conditions with self-similar vacuum mode spectra, dynamic Casimir probing at the fundamental mode cutoff via piezoelectric gap oscillation, and hysteresis measurements to test for non-conservative vacuum interactions. The regime is designed to yield publication-quality results regardless of outcome: a null result produces direct experimental bounds on boundary-dependent vacuum optical response, while a positive anomaly triggers a rigorous verification protocol. All procedures are executable with a tabletop apparatus costing under \2,500. Target venue: Physical Review A. Author preprint deposited for archival and citation. Draft — pending author review.