For 3+ player matches, ZoneMinRadius was 3 (zone diameter 6) but attack
radius is only 3.5 tiles (AttackRadius2=12). Bots at opposite edges of
the final zone were 6 tiles apart - well outside attack range - allowing
energy farming without forced combat.
Set ZoneMinRadius=1 for 3+ player (zone diameter 2 < attack radius 3.5),
guaranteeing any two bots in the final zone are within attack range.
Tested with acb-local: 6-player match now shows combat_deaths>0 for all
players. 2-player unchanged (ZoneMinRadius=3, attack radius 6).
Closes: bf-1qg4
c80a02f39b