Quantum Mechanics as Fiber Projection: Propagators, $\sigma$-Localization, and Measurement Baths

Develops a complementary geometric lane: states live on $M_4\times K$ and 4D observations are obtained by projection/partial trace over $K$. Proves a zero-mode propagator correspondence and formulates $\sigma$ as a KK spectral filter (heat-kernel proxy). Specifies minimal Lindblad bath models (spectral vs position monitoring) and connects them to effective $\sigma$ dynamics. Closes sanity checks for double-slit interference (zero-mode recovery + finite-mode visibility estimate) and Born-rule consistency (4D probabilities as marginals of the $L^2$ measure).For a series overview, reading order, and claim‑hygiene guide, see Coherent Gravity Theory (CGT): An Onboarding Primer: https://doi.org/10.5281/zenodo.18212967