fix(decision): add missing actions to AI prompt (#983)

问题：AI 返回 adjust_stop_loss 导致决策验证失败
根因：prompt 只列出 6 个 action，缺少 3 个有效 action

修复（TDD）：
1. 添加测试验证 prompt 包含所有 9 个有效 action
2. 最小修改：在 action 列表中补充 3 个缺失项
   - update_stop_loss
   - update_take_profit
   - partial_close

测试：
- TestBuildSystemPrompt_ContainsAllValidActions ✅
- TestBuildSystemPrompt_ActionListCompleteness ✅

Fixes: 无效的action: adjust_stop_loss

decision/engine.go

@@ -350,7 +350,7 @@ func buildSystemPrompt(accountEquity float64, btcEthLeverage, altcoinLeverage in
 	sb.WriteString("]\n```\n")
 	sb.WriteString("</decision>\n\n")
 	sb.WriteString("## 字段说明\n\n")
-	sb.WriteString("- `action`: open_long | open_short | close_long | close_short | hold | wait\n")
+	sb.WriteString("- `action`: open_long | open_short | close_long | close_short | update_stop_loss | update_take_profit | partial_close | hold | wait\n")
 	sb.WriteString("- `confidence`: 0-100（开仓建议≥75）\n")
 	sb.WriteString("- 开仓时必填: leverage, position_size_usd, stop_loss, take_profit, confidence, risk_usd, reasoning\n\n")
 

decision/prompt_test.go

@@ -0,0 +1,50 @@
+package decision
+
+import (
+	"strings"
+	"testing"
+)
+
+// TestBuildSystemPrompt_ContainsAllValidActions 测试 prompt 是否包含所有有效的 action
+func TestBuildSystemPrompt_ContainsAllValidActions(t *testing.T) {
+	// 这是系统中定义的所有有效 action（来自 validateDecision）
+	validActions := []string{
+		"open_long",
+		"open_short",
+		"close_long",
+		"close_short",
+		"update_stop_loss",
+		"update_take_profit",
+		"partial_close",
+		"hold",
+		"wait",
+	}
+
+	// 构建 prompt
+	prompt := buildSystemPrompt(1000.0, 10, 5, "default")
+
+	// 验证每个有效 action 都在 prompt 中出现
+	for _, action := range validActions {
+		if !strings.Contains(prompt, action) {
+			t.Errorf("Prompt 缺少有效的 action: %s", action)
+		}
+	}
+}
+
+// TestBuildSystemPrompt_ActionListCompleteness 测试 action 列表的完整性
+func TestBuildSystemPrompt_ActionListCompleteness(t *testing.T) {
+	prompt := buildSystemPrompt(1000.0, 10, 5, "default")
+
+	// 检查是否包含关键的缺失 action
+	missingActions := []string{
+		"update_stop_loss",
+		"update_take_profit",
+		"partial_close",
+	}
+
+	for _, action := range missingActions {
+		if !strings.Contains(prompt, action) {
+			t.Errorf("Prompt 缺少关键 action: %s（这会导致 AI 返回无效决策）", action)
+		}
+	}
+}