fix: preserve gameplay data and correct duel evaluation

- Preserve snake customizations across database migrations and merges.
- Lazily load optional storage backends for SQLite maintenance scripts.
- Match Apex territory and nearest-food tie-breaking semantics.
- Resolve duel occupancy after simultaneous movement and food growth.
- Recompute simulated head-to-head danger after body growth.
- Add regression coverage and declare the aiofiles dependency.

snakes/__init__.py

@@ -11,7 +11,7 @@ SNAKE_REGISTRY = {
   "UltimateBattleSnake": "4.5.0",
   "ApexBattleSnake": "1.0.0",
   "SupremeBattleSnake_ClaudeOpus4_6": "1.0.0",
-  "PrismBattleSnake_GPT_5_6_Sol": "1.0.0",
+  "PrismBattleSnake_GPT_5_6_Sol": "1.0.1",
 }
 
 DEFAULT_SNAKE_CONFIG = {