Path calculator now queries Microsoft Building Footprints for the
tallest structure within 80m of each profile sample and renders a red
"Buildings" dataset on top of the terrain layer in the elevation chart.
Also normalize on-disk grid HRRR cells to include the legacy
:min_refractivity_gradient / :surface_refractivity / :ducting_detected
keys (mapped from :native_min_gradient and :duct_count). Path-calculator
crashed in prod with KeyError when a path's HRRR points came from the
new on-disk grid format instead of the DB profile shape.