Fix inference.py to match sample script exactly: HF_TOKEN var name, no fallback

inference.py

@@ -31,7 +31,7 @@ from openai import OpenAI
 # ---------------------------------------------------------------------------
 
 API_BASE_URL = os.getenv("API_BASE_URL", "https://api.groq.com/openai/v1")
-API_KEY = os.getenv("HF_TOKEN") or os.getenv("API_KEY")
+HF_TOKEN = os.getenv("HF_TOKEN")
 MODEL_NAME = os.getenv("MODEL_NAME", "llama-3.3-70b-versatile")
 ENV_URL = os.getenv("ENV_URL", "http://localhost:7860")
 ENV_NAME = "sevzero"
@@ -376,7 +376,7 @@ def run_episode(
 
 
 def main() -> None:
-    client = OpenAI(base_url=API_BASE_URL, api_key=API_KEY)
+    client = OpenAI(base_url=API_BASE_URL, api_key=HF_TOKEN)
 
     all_tasks = {"easy": 42, "medium": 123, "hard": 7}
     task_filter = os.getenv("TASKS", "").strip()