Extract the hunt-region engine adapter

[adrunkhuman]

Summary

• Move hunt-region cache ownership and direct map, spawn, player, spell, configuration, and weapon access into PlayerBotHuntRegionAdapter.
• Preserve the existing planner and policy-helper APIs as forwarding contracts, with no caller changes.

Verification

• docker compose -f server/compose.yaml build server - passed
• Focused hunt-region planning, adaptive challenge, readiness, equipment-offer, and magic-training scenarios - 5/5 passed