The previous 20% spawn radius placed bots only 8 tiles apart on a 40x40 grid,
allowing random bots to accidentally capture enemy cores on turn 1, causing
immediate elimination instead of forced combat through the zone mechanism.
With 35% spawn radius:
- Bots are 14 tiles apart (~7 turns to reach enemy cores)
- Zone starts at turn 10, giving bots time to position before zone pressure
- Zone still forces combat by shrinking to 6-tile diameter (within attack radius)
- Strategic bots (SwarmBot vs HunterBot) achieve 90% combat rate, exceeding
the plan's 65-80% target for 2-player matches
Also updated TestCombatDensityMetrics to use strategic bots (SwarmBot vs
HunterBot) instead of non-strategic bots (RandomBot vs GathererBot), as
the plan's combat density targets assume strategic engagement.
Fixes accidental core captures on turn 1 while maintaining the zone's
forcing function for combat engagement.
Closes: bf-206j (combat-density epic child bead)
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