test: speed up CI and harden the suite

tests/providers/test_responses_circuit_breaker.py

@@ -5,9 +5,9 @@ import time
 import pytest
 
 from nanobot.providers.openai_compat_provider import (
-    OpenAICompatProvider,
     _RESPONSES_FAILURE_THRESHOLD,
     _RESPONSES_PROBE_INTERVAL_S,
+    OpenAICompatProvider,
 )