Revert "Mouse event scaling with map" and "Map scaling" for brokenness

Only a portion of the map is visible, making the game unplayable.

This reverts commits d6523cf24eb12af8175a5bdca608f3dd9032c925 and
62122efd0e0adb1777e6b0d518315bb49dd0d092.
Pathfinding

The game talks to an Emscripten-compiled C++ layer, which does
pathfinding through Dijkstra's algorithm (for speed!).