Variable SHARED_EDGE_RAY_CATEGORIES`Const`

SHARED_EDGE_RAY_CATEGORIES: readonly [
    "exact vertical ray on a grid line",
    "oblique ray at a grid-line edge",
    "oblique ray at a diagonal edge",
    "oblique ray at an interior vertex",
] = ...

What each ray of sharedEdgeRays is aimed at, by its categories entry.