fix(track): the shared running surface ends along the edge of the treads of the wheels of the other track, not across the rail: on a nose leg the edge runs aslant over the head, on a stock rail it follows the curve of the other path; only the top of the head takes the other texture, the rest of the rail keeps its own

world/Track.h

@@ -399,6 +399,8 @@ public:
         double to { 0.0 };
         material_handle material { 0 };
         int anchor { 0 };
+        std::vector<glm::dvec2> edge;
+        bool below { false };
     };
     struct rail_layout {
         rail_plan plans[ 2 ][ 2 ]; // path, right side