Default every role to openai/gpt-oss-120b

Roll back the gpt-oss-20b default on file/normalizer roles. All roles
now default to openai/gpt-oss-120b (the only model confirmed working
on this account); env-var overrides remain for later diversification.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019ryPUj8AtsFopnufGRSc4L

agents.py

@@ -20,10 +20,10 @@ def _make_llm(model: str = "openai/gpt-oss-120b", temperature: float = 0.1) -> C
 #     -H "Authorization: Bearer $GROQ_API_KEY" | jq '.data[].id'
 _ROLE_MODELS = {
     "web": os.getenv("GROQ_WEB_MODEL", "openai/gpt-oss-120b"),
-    "file": os.getenv("GROQ_FILE_MODEL", "openai/gpt-oss-20b"),
+    "file": os.getenv("GROQ_FILE_MODEL", "openai/gpt-oss-120b"),
     "media": os.getenv("GROQ_MEDIA_MODEL", "openai/gpt-oss-120b"),
     "code": os.getenv("GROQ_CODE_MODEL", "openai/gpt-oss-120b"),
-    "normalizer": os.getenv("GROQ_NORMALIZER_MODEL", "openai/gpt-oss-20b"),
+    "normalizer": os.getenv("GROQ_NORMALIZER_MODEL", "openai/gpt-oss-120b"),
 }