feat: 新增slope_r2因子并切换为默认因子（年化19.84%, 夏普1.14）

- simple_rotation.py: 新增3种score函数（vol_adjusted_momentum, slope_r2, momentum）
- config_loader.py: FactorType枚举新增VOL_ADJUSTED_MOMENTUM
- config_simple.yaml: factor.type 切换为 slope_r2
- experiments/factor_comparison.py: 4种因子对比实验脚本
- experiments/output: 实验结果（slope_r2全面胜出）

rotation/experiments/output/factor_comparison_results.json

@@ -0,0 +1,45 @@
+{
+  "timestamp": "2026-06-06T15:41:51.261231",
+  "results": [
+    {
+      "factor_type": "weighted_momentum",
+      "annual_return": 0.1836425584586039,
+      "total_return": 1.8188636662013202,
+      "sharpe_ratio": 1.0221559991160554,
+      "max_drawdown": -0.16355913241141637,
+      "win_rate": 0.539754363283775,
+      "rebalance_count": 405,
+      "calmar_ratio": 1.1227900010906742
+    },
+    {
+      "factor_type": "vol_adjusted_momentum",
+      "annual_return": 0.1315526234967641,
+      "total_return": 1.1376143317727325,
+      "sharpe_ratio": 0.8543126134924596,
+      "max_drawdown": -0.18613474523686568,
+      "win_rate": 0.5585003232062056,
+      "rebalance_count": 393,
+      "calmar_ratio": 0.7067601662943525
+    },
+    {
+      "factor_type": "slope_r2",
+      "annual_return": 0.198416094188119,
+      "total_return": 2.0421974188211456,
+      "sharpe_ratio": 1.1350010914615083,
+      "max_drawdown": -0.15352659557851117,
+      "win_rate": 0.541343669250646,
+      "rebalance_count": 394,
+      "calmar_ratio": 1.2923890707043786
+    },
+    {
+      "factor_type": "momentum",
+      "annual_return": 0.09270306870862322,
+      "total_return": 0.7245114082990154,
+      "sharpe_ratio": 0.5741296434738409,
+      "max_drawdown": -0.17419361103962644,
+      "win_rate": 0.5326438267614738,
+      "rebalance_count": 729,
+      "calmar_ratio": 0.5321840919156022
+    }
+  ]
+}