[codex] Add Firebat Naxx self-play bot

[MaxResnick]

Summary

• Add Firebat Naxx Combo Druid vs Zoo Warlock card/deck support and matchup tests
• Add policy/value, MCTS, random/self-play rollout generation, training, benchmark, and terminal viewer tools
• Add local dashboard and checkpoint scheduler for parallel self-play monitoring

Validation

• dotnet build core-extensions/SabberStoneBasicAI/SabberStoneBasicAI.csproj -f net10.0 --no-restore
• python3 -m py_compile tools/train_firebat_value.py tools/firebat_selfplay_dashboard.py tools/firebat_checkpoint_scheduler.py
• dotnet test SabberStoneCoreTest/SabberStoneCoreTest.csproj -f net10.0 --no-restore --filter FullyQualifiedName~FirebatNaxxMatchupTest

Notes

• Generated runtime data under data/ was intentionally not committed.