This preprint (arXiv:2605.20221, not yet peer-reviewed) inverts the usual Morris-Thorne wormhole construction by deriving the metric functions directly from NGC 3198's observed rotation curve using 43 SPARC data points spanning 0.32-44 kpc at 13.8 Mpc distance. Four halo profiles were fitted via Nelder-Mead chi-squared minimization; the cored Burkert profile yields the lowest reduced chi-squared of 2.545 and produces the strongest central null-energy-condition violation, while cuspy NFW and Hernquist profiles do not. The resulting dimensionless wormhole indicator remains below 10^-6 across the observed domain, satisfying flare-out by many orders of magnitude. What prior coverage overlooks is that this approach implicitly tests whether galactic dark-matter halos could be reinterpreted as the exterior regions of macroscopic, traversable wormholes without invoking additional exotic matter beyond the fitted density. Limitations include the assumption of static spherical symmetry and the absence of stability analysis against perturbations; future work could incorporate Gaia proper-motion data or compare against other SPARC galaxies to test generality.