Zero cursor location with BackSpace, too
Fix getArenaUI vs viewedLevel
Get rid of the targetting prompt
Display the length of targetting path and line
Stop when an item spotted and point cursor at it

unless cursor points at an actor, e.g., an enemy.
Optimize accesses to BFS a tiny bit
Replace actorSeesPos with BFS everywhere
Get rid of per-actor perception

Now BFS distances give almost the same information
(or even better, because they determine if a tile can be shot,
as opposed to seen).
Make BFS data lazy (it turns out, it wasn't before)