Define the combat arena dungeon cave for skirmish and PvP scenarios
Don't let stairs and scrolls point outside the dungeon

This is needed to prevent scrolls from prematurely ending a deathmatch.
TODO: instead introduce 'exits' that let you escape the dungeon.
Fix an assertion failure when immediately saving a game with --allClear
Add a Quit effect, separate from the staircase effects
Allow multiple effects for the same UI command
Place a Quit tile on level 1 of long dungeons only
Refactor reacquireTgt
Simplify AI visible foes calculation
Make actors smarter, for the symmetric skirmish scenario
Let AI switch leaders

See the skirmish mode, where switching leaders makes sense.
Add a dungeon defense scenario (player-controlled monsters)
Fix the verification of Effect.Quit feature trigger
Specify the Effect.Quit feature per-dungeon in the rules config
Help hero AI to win the game (go down, exit the dungeon)
Don't let dungeon defenders win via the Quit feature