chore(agent-runner): split litellm usage details

tests/unit_tests/provider/test_litellmchat.py

@@ -115,15 +115,6 @@ class TestExtractUsage:
         assert result['prompt_tokens'] == 0
         assert result['completion_tokens'] == 0
 
-    def test_extract_usage_without_provider_usage(self):
-        """Missing provider usage is not treated as authoritative zero usage."""
-        requester = litellmchat.LiteLLMRequester(ap=Mock(), config={})
-
-        response = Mock()
-        response.usage = None
-
-        assert requester._extract_usage(response) is None
-
 
 class TestNormalizeUsage:
     """Test _normalize_usage helper covering real-world usage shapes"""
@@ -140,22 +131,6 @@ class TestNormalizeUsage:
         )
         assert result == {'prompt_tokens': 12, 'completion_tokens': 8, 'total_tokens': 20}
 
-    def test_preserves_token_details(self):
-        """Provider token details such as cache counters are preserved."""
-        result = litellmchat.LiteLLMRequester._normalize_usage(
-            {
-                'prompt_tokens': 12,
-                'completion_tokens': 8,
-                'total_tokens': 20,
-                'prompt_tokens_details': {'cached_tokens': 7},
-                'completion_tokens_details': {'reasoning_tokens': 3},
-            }
-        )
-
-        assert result['prompt_tokens'] == 12
-        assert result['prompt_tokens_details'] == {'cached_tokens': 7}
-        assert result['completion_tokens_details'] == {'reasoning_tokens': 3}
-
     def test_missing_total_is_derived(self):
         """When total_tokens is absent/zero it is derived from prompt + completion"""
         usage = Mock()