Remove some commented-out code
Show player coords on the lower-left.

For compatibility with the editor, which uses the upper-left.
[player] make @reset_point a Vec2
[player] click_area is around @start
[camera] allow free camera control
[editor] Move all edit-related stuff into editor.
[editor] Editor camera follows the mouse.
[editor] Allow selecting objects
[boundary] give boundary a click_area
[editor] Prioritize selecting objects with lower t