Snap belt-drag end tile to a building's input edge

src/ui/GameWorldView.h

@@ -279,6 +279,9 @@ private:
     // on release. Empty unless a belt drag is in progress.
     std::vector<BeltPathTile>            m_beltDragPath;
     QPoint                               m_beltDragAnchor;
+    // Last known cursor position in world (tile) units; used to pick the belt-drag
+    // end tile closest to the cursor when snapping to a building (REQ-BLD-BELT-DRAG).
+    QVector2D                            m_cursorWorldPos;
     bool                                 m_dragging;
 
     std::optional<Blueprint> m_blueprintMode;