fix: prompt_override 경로 _total_decisions 미카운트, 완료 로그 추가, 테스트 보완

리뷰 지적 사항 반영:
- _total_decisions 카운트 제거 (플레이북 생성은 거래 결정이 아님 → 메트릭 왜곡 방지)
- "Gemini raw response received" INFO 로그 추가 (완료 추적 가능)
- test_prompt_override_takes_priority_over_optimization 신규 추가
  (enable_optimization=True 상태에서도 prompt_override 우선됨을 검증)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/brain/gemini_client.py

@@ -445,7 +445,10 @@ class GeminiClient:
         # not a parsed TradeDecision. Skip parse_response to avoid spurious
         # "Missing fields" warnings and return the raw response directly. (#247)
         if "prompt_override" in market_data:
-            self._total_decisions += 1
+            logger.info(
+                "Gemini raw response received (prompt_override, tokens=%d)", token_count
+            )
+            # Not a trade decision — don't inflate _total_decisions metrics
             return TradeDecision(
                 action="HOLD", confidence=0, rationale=raw, token_count=token_count
             )

tests/test_brain.py

@@ -360,6 +360,36 @@ class TestPromptOverride:
                 # Raw playbook JSON preserved in rationale
                 assert decision.rationale == playbook_json
 
+    @pytest.mark.asyncio
+    async def test_prompt_override_takes_priority_over_optimization(self, settings):
+        """prompt_override must win over enable_optimization=True."""
+        client = GeminiClient(settings)
+        client._enable_optimization = True
+
+        custom_prompt = "Explicit playbook prompt"
+
+        mock_response = MagicMock()
+        mock_response.text = '{"market_outlook": "neutral", "stocks": []}'
+
+        with patch.object(
+            client._client.aio.models,
+            "generate_content",
+            new_callable=AsyncMock,
+            return_value=mock_response,
+        ) as mock_generate:
+            market_data = {
+                "stock_code": "PLANNER",
+                "current_price": 0,
+                "prompt_override": custom_prompt,
+            }
+            await client.decide(market_data)
+
+            actual_prompt = mock_generate.call_args[1].get(
+                "contents", mock_generate.call_args[0][1] if len(mock_generate.call_args[0]) > 1 else None
+            )
+            # The custom prompt must be used, not the compressed prompt
+            assert actual_prompt == custom_prompt
+
     @pytest.mark.asyncio
     async def test_without_prompt_override_uses_build_prompt(self, settings):
         """Without prompt_override, decide() should use build_prompt as before."""