Metastable Membrane Dynamics in Finite-Observer Coherence Networks: A Conservative Numerical Study of Few-Percent Coherence Spread, Threshold Support, Adaptive Recovery, Shell Response, and Residual Texture

Classical spacetime is modeled as a metastable thermodynamic membrane maintained by coherence production against dissipation, boundary-mediated uncertainty leakage, and mismatch. The model uses finite observer domains, overlap-defined coherence, an admissibility threshold, record accumulation, and a local response function affecting effective gravitational response near threshold. This paper reports a conservative numerical study of thresholded finite-observer coherence networks. The central result is not a single universal percentage, but a structured metastable package: percent-level coherence spread, active support above threshold, record feedback, seed robustness, adaptive recovery after injury, shell-localized response, and correlated residual texture. Null and ablation controls show that generic noisy smoothing can reproduce a numerical spread but not the full thresholded, record-bearing active regime. Shell-extraction tests show that isolated threshold islands produce effective gravitational response profiles well described by a log-Gaussian shell form, while healthier active corridors weaken and distribute the response across membrane holes and ridges. The paper does not claim to derive the baryon fraction, solve dark matter, or reproduce the acoustic physics of the cosmic microwave background. The few-percent spread is treated as a robust balance-window signature whose cosmological significance remains open. CMB-style diagnostics are presented only as texture-level residual comparisons, not as an acoustic CMB derivation.