feat(progress): count creeper explosion encounters

design/architecture.md

@@ -30,6 +30,8 @@ Player progress is loaded into an online cache before synchronous aura decisions
 
 A creeper death is attributed to a player when the player directly dealt the final damage or is attributable through a projectile or owned tameable. The progression service deduplicates a creeper death and records one point.
 
+A self-destructing creeper also awards one point to every player its explosion would have hit. Explosion awards are deduplicated independently for each creeper and player, count before armor or aura mitigation, and use the same feedback as credited kills.
+
 For explosions, player damage events establish whether an unlocked player would have been hit before armor mitigation. Each protected player receives their own rank multiplier. If any aura activates, the corresponding creeper explosion's affected block list is cleared for everyone. Rank VI cancels the player's damage event entirely.
 
 ## Commands and configuration