fix(textarena): use relative import in rewards

Use a package-relative models import in textarena rewards to avoid import resolution failures.

Author: miniMaddy

envs/textarena_env/rewards.py

@@ -5,10 +5,7 @@
 import re
 from typing import Dict, List, Protocol, Tuple
 
-try:
-    from textarena_env.models import TextArenaAction, TextArenaObservation
-except ImportError:
-    from models import TextArenaAction, TextArenaObservation
+from .models import TextArenaAction, TextArenaObservation
 
 
 class RewardProvider(Protocol):