Channel-Calibrated Harmonic Entanglement Certificates Under Loss and Phase Noise

We study the survival of phase-sensitive entanglement in a two-mode-squeezed pair under local Gaussian noise and pair-phase randomization. For the preparation-then-additive model with independent single-quadrature diffusion, we derive an exact Gaussian criterion: in the convention [q,p]=i and vacuum variance 1/2, the state is NPT if and only if d_+ d_- < sinh^2(2r). For unequal thermal attenuators followed by an arbitrary circular phase law with characteristic coefficients chi_d, a locally filtered Fock block has a negative eigenvalue if and only if |chi_d| > tau^d, with tau determined by the output occupations, anomalous coherence, and determinant of the filtered Gaussian core. This provides a sufficient certificate of full-state NPT and one-copy distillability, but not a complete infinite-dimensional PPT criterion. The analysis identifies finite-order harmonic blind spots, a composable detectability radius under independent phase noise, and calibration rules based on number-resolved coherences. We also give a time-ordered Lyapunov treatment of simultaneous squeezing and diffusion and a conditional de Sitter-to-observable transfer protocol whose interpretation depends on the specified bath, mode basis, transfer functions, and detector likelihood.