CSF-CMT vΩ.25.1: Photon Medium Proof from A Priori Field-Medium and Continuity Conditions

Standard physics asserts that energy E=mc^2 released from matter annihilation can convert into photons—massless, charge-less quanta—without passing through any physical substrate. This paper proves, from two a priori conditions independent of the CSF-CMT framework, that this assertion is epistemologically untenable. The Field-Medium Thesis and the Field Continuity Thesis jointly entail that photons must be coarse-grained excitations of a continuous first-space substrate. The causal chain is derived: matter annihilation \rightarrow energy reflux into the first-space initial state \Psi_I^{(0)} \rightarrow excitation of the string-electromagnetic mode \chi_{\text{string}}^{\text{EM}} \rightarrow coarse-graining at L_c \sim \lambda_C \rightarrow photon. Three objective falsifiability criteria are provided, distinguishing this prediction from standard quantum electrodynamics.