feat(strategy): 实现策略层与配置加载

核心组件：
- StrategyBase: 策略抽象基类（含回调钩子）
  - 类属性（可被配置覆盖）
  - init_factors(): 初始化因子组合
  - init_signal_generator(): 初始化信号生成器
  - run(): 运行策略
- RotationStrategy: 轮动策略示例实现
  - 动量因子 + TopN选股
  - before_entry回调（溢价过滤）
  - dynamic_stoploss回调（持仓时间动态止损）
- ConfigLoader: 配置加载器（YAML支持）
- StrategyConfig: 策略配置数据类

特点：
- 配置覆盖类属性
- 回调自动注册
- 策略工厂模式

测试覆盖：8个测试全部通过

framework/tests/test_strategy.py

@@ -0,0 +1,140 @@
+"""
+策略与配置层测试
+"""
+
+import pytest
+import pandas as pd
+import numpy as np
+from datetime import datetime
+
+from framework.strategy import StrategyBase, ConfigLoader, RotationStrategy
+from framework.factors import FactorRegistry
+from framework.factors.momentum import MomentumFactor
+from framework.risk import Position
+
+
+class TestStrategyBase:
+    """测试策略基类"""
+    
+    def test_strategy_attributes(self):
+        """测试策略属性"""
+        strategy = RotationStrategy()
+        assert strategy.name == "rotation"
+        assert strategy.select_num == 3
+        assert strategy.stoploss == -0.05
+    
+    def test_config_override(self):
+        """测试配置覆盖"""
+        config = {
+            'params': {
+                'select_num': 5,
+                'stoploss': -0.08
+            }
+        }
+        
+        strategy = RotationStrategy(config=config)
+        assert strategy.select_num == 5
+        assert strategy.stoploss == -0.08
+    
+    def test_factor_initialization(self):
+        """测试因子初始化"""
+        strategy = RotationStrategy()
+        factors = strategy.init_factors()
+        
+        assert factors is not None
+        assert len(factors.factors) == 1
+    
+    def test_signal_generator_initialization(self):
+        """测试信号生成器初始化"""
+        strategy = RotationStrategy()
+        signal_gen = strategy.init_signal_generator()
+        
+        assert signal_gen is not None
+        assert signal_gen.select_num == 3
+    
+    def test_strategy_run(self):
+        """测试策略运行"""
+        strategy = RotationStrategy()
+        
+        # 生成测试数据（需要'close'列）
+        dates = pd.date_range('2020-01-01', periods=100)
+        data = pd.DataFrame({
+            'close': np.random.randn(100).cumsum() + 100,
+            'code1': np.random.randn(100).cumsum() + 100,
+            'code2': np.random.randn(100).cumsum() + 100,
+            'code3': np.random.randn(100).cumsum() + 100,
+        }, index=dates)
+        
+        result = strategy.run(data)
+        
+        assert 'signal' in result.columns
+        assert len(result) == len(data)
+
+
+class TestRotationStrategy:
+    """测试轮动策略"""
+    
+    def test_before_entry_callback(self):
+        """测试入场前回调"""
+        strategy = RotationStrategy()
+        
+        # 溢价正常，允许入场
+        result = strategy.before_entry('code1', 100.0, premium=0.05)
+        assert result == True
+        
+        # 溢价过高，拒绝入场
+        result = strategy.before_entry('code1', 100.0, premium=0.15)
+        assert result == False
+    
+    def test_dynamic_stoploss_callback(self):
+        """测试动态止损回调"""
+        strategy = RotationStrategy()
+        
+        # 持仓5天
+        position = Position(
+            code='code1',
+            entry_price=100.0,
+            entry_date=datetime(2020, 1, 1),
+            current_price=95.0,
+            current_date=datetime(2020, 1, 6),  # 5天后
+            quantity=100,
+            weight=0.33
+        )
+        stoploss = strategy.dynamic_stoploss(position)
+        # holding_days=5，返回-0.05
+        assert stoploss == -0.05
+
+
+class TestConfigLoader:
+    """测试配置加载器"""
+    
+    def test_load_from_yaml_string(self):
+        """测试从YAML字符串加载"""
+        yaml_str = """
+strategy:
+  name: test_strategy
+  version: 1
+
+factors:
+  - name: momentum
+    weight: 1.0
+    params:
+      n_days: 25
+
+signal:
+  mode: top_n
+  select_num: 3
+
+params:
+  stoploss: -0.05
+"""
+        
+        config = ConfigLoader.from_yaml(yaml_str)
+        
+        assert config['strategy']['name'] == 'test_strategy'
+        assert config['factors'][0]['name'] == 'momentum'
+        assert config['signal']['select_num'] == 3
+
+
+if __name__ == '__main__':
+    pytest.main([__file__, '-v'])