/usr/include/planarity/ is in libplanarity-dev 3.0.0.5-1+b1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/planarity/appconst.h
/usr/include/planarity/graph.h
/usr/include/planarity/graphDrawPlanar.h
/usr/include/planarity/graphDrawPlanar.private.h
/usr/include/planarity/graphExtensions.h
/usr/include/planarity/graphExtensions.private.h
/usr/include/planarity/graphFunctionTable.h
/usr/include/planarity/graphK23Search.h
/usr/include/planarity/graphK23Search.private.h
/usr/include/planarity/graphK33Search.h
/usr/include/planarity/graphK33Search.private.h
/usr/include/planarity/graphK4Search.h
/usr/include/planarity/graphK4Search.private.h
/usr/include/planarity/graphStructures.h
/usr/include/planarity/listcoll.h
/usr/include/planarity/planarity.h
/usr/include/planarity/platformTime.h
/usr/include/planarity/stack.h