GR–QC Bridge via Spacetime Safety Equation: Multi-channel Verification of Blackfield and Observational Scalar αBF

Preprint. Publicly released on Zenodo prior to journal submission.This preprint develops an operational bridge between general relativity and quantum mechanics via a minimal observational-layer update encoded by a single scalar parameter αBF\alpha_{\mathrm{BF}}αBF, without introducing new degrees of freedom. It establishes a compact dictionary ln⁡(1+αBF)=ε/π\ln(1+\alpha_{\mathrm{BF}})=\varepsilon/\piln(1+αBF)=ε/π linking geometric rescaling to phase-readout calibration, and constrains αBF\alpha_{\mathrm{BF}}αBF using three channels: quantum-optical bright/dark interference, the EHT ring diameter of Sgr A*, and gravitational-wave ringdown / quasi-normal-mode tests (GWTC-3).