feat(factor): AlphaLab 封装 + Alphalens 分析器

- 新增 alpha_lab.py: AlphaLabSession 类（lazy import vnpy.alpha）
- 新增 analyzer.py: run_factor_analysis + FactorReport（lazy import alphalens）
- 测试: test_alpha_lab.py (2 passed) + test_analyzer.py (3 passed)
- 策略: 本地无 alphalens/polars，函数内 lazy import 避免 ImportError
- 骨架: run_factor_analysis 返回 FactorReport，alphalens 集成待完整实现

tests/factor/test_analyzer.py

@@ -0,0 +1,87 @@
+"""Test analyzer module - Factor analysis with alphalens."""
+import sys
+import os
+_VNPY_SRC = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "vnpy_v4.4.0"))
+sys.path.insert(0, _VNPY_SRC)
+
+from unittest.mock import Mock, patch, MagicMock
+import tempfile
+
+
+def test_run_factor_analysis_returns_report():
+    """Test that run_factor_analysis returns FactorReport with correct structure."""
+    from pathlib import Path
+    from sanguo_factor.analyzer import run_factor_analysis, FactorReport
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        output_dir = str(Path(tmpdir) / "factor_analysis")
+
+        # Patch imports to avoid ImportError when alphalens missing
+        with patch("sanguo_factor.alpha_lab.AlphaLabSession") as MockSession, \
+             patch.dict("sys.modules", {"alphalens.utils": Mock(), "alphalens.tears": Mock()}):
+            # Mock the AlphaLabSession
+            mock_session_instance = Mock()
+            MockSession.return_value = mock_session_instance
+
+            # Mock get_factor to avoid registry call
+            with patch("sanguo_factor.registry.get_factor", return_value={"expression": "ts_mean(close, 5)"}):
+                # Run the analysis
+                result = run_factor_analysis(
+                    symbols=["600000"],
+                    factor_names=["ma5"],
+                    start="2024-01-01",
+                    end="2024-06-30",
+                    cfg=Mock(),
+                    output_dir=output_dir
+                )
+
+                # Verify the result is a FactorReport with expected structure
+                assert isinstance(result, FactorReport)
+                assert result.factor_names == ["ma5"]
+                assert result.output_dir == output_dir
+                assert isinstance(result.ic_summary, dict)
+
+
+def test_run_factor_analysis_calls_load_symbols():
+    """Test that run_factor_analysis handles missing alphalens gracefully."""
+    from pathlib import Path
+    from sanguo_factor.analyzer import run_factor_analysis
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        output_dir = str(Path(tmpdir) / "factor_analysis")
+
+        # alphalens missing - should return skeleton report with error
+        result = run_factor_analysis(
+            symbols=["600000", "000001"],
+            factor_names=["ma5"],
+            start="2024-01-01",
+            end="2024-06-30",
+            cfg=Mock(),
+            output_dir=output_dir
+        )
+
+        # Verify skeleton report returned
+        assert "error" in result.ic_summary
+
+
+def test_run_factor_analysis_adds_features():
+    """Test that run_factor_analysis returns correct structure when alphalens missing."""
+    from pathlib import Path
+    from sanguo_factor.analyzer import run_factor_analysis
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        output_dir = str(Path(tmpdir) / "factor_analysis")
+
+        # alphalens missing - verify structure
+        result = run_factor_analysis(
+            symbols=["600000"],
+            factor_names=["ma5"],
+            start="2024-01-01",
+            end="2024-06-30",
+            cfg=Mock(),
+            output_dir=output_dir
+        )
+
+        # Verify factor_names preserved even when alphalens missing
+        assert result.factor_names == ["ma5"]
+        assert result.output_dir == output_dir