fix(core): map Anthropic 'refusal' finish reason to 'content_filter'

Anthropic's 'refusal' stop_reason was missing from _FINISH_REASON_MAP,
causing it to fall through to the default 'stop' — hiding the fact that
the model refused to respond due to safety policies.

Fixes #23793

litellm/litellm_core_utils/core_helpers.py

@@ -64,6 +64,7 @@ _FINISH_REASON_MAP: dict[str, OpenAIChatCompletionFinishReason] = {
     "end_turn": "stop",
     "max_tokens": "length",
     "tool_use": "tool_calls",
+    "refusal": "content_filter",
     "compaction": "length",
     # Cohere
     "COMPLETE": "stop",

tests/test_litellm/litellm_core_utils/test_core_helpers.py

@@ -74,6 +74,9 @@ class TestMapFinishReasonAnthropic:
     def test_compaction(self):
         assert map_finish_reason("compaction") == "length"
 
+    def test_refusal(self):
+        assert map_finish_reason("refusal") == "content_filter"
+
 
 class TestMapFinishReasonGemini:
     @pytest.mark.parametrize(