Use episode wording for neutral forfeit scores

[KyleHerndon]

Summary

• Reword mean-score leaderboard mechanics to describe episode scores rather than saying episodes are rounds.
• Rename the neutral-score regression test to use episode terminology.

Validation

• git diff --check
• uv run pytest tests/test_commissioner_strategies.py -q

[KyleHerndon]

Closing this follow-up: the terminology concern was for Cue-n-Woo replay/docs, not commissioner wording.