refactor(swap): EQD-6977 拆分 CalcPenalty 计息分支提升可读性

将 CalcPenalty 内复利/单利两个 if/else 大块抽为 AccrueCompound/AccrueSimple 私有方法(返回 (accrued, finalBasis))，主体只表达分派+组装事件。签名与行为零变化，Penalty 套件 11/11 通过。

YLErpDAL/Modules/SwapModule/Penalty/SwapPenaltyInterestCalculator.cs

@@ -69,50 +69,13 @@ public static class SwapPenaltyInterestCalculator
         var boundary = AccrualBoundary.Of(includeStart: !unwindDaySettled, includeEnd: maturityCalcLast);
         var allInRate = frozenRate.AllInRate;
 
-        decimal amount;
-        decimal finalBasis;
-        if (policy.IsCompound)
-        {
-            // 复利：即使利率冻结为单值，也须按重置日分段（并本金发生在分段边界），每段同一冻结利率。
-            // notional = 本金 + 已并入最近重置日的利息：全期轨迹中当前重置段的滚动基数，
-            // 段内（含罚息窗口首段）每一天都在其上计息——平仓日落在段中间时与全期逐日对齐的关键。
-            var segments = BuildFrozenSegments(unwindDate, maturityDate, policy.ResetPeriodDays, resetAnchor, allInRate);
-            var r = CompoundInterestAccrual.AccruePeriod(
-                notional: closePrincipal + capitalizedInterest,
-                segmentRates: segments,
-                startDate: unwindDate,
-                endDate: maturityDate,
-                boundary: boundary,
-                annualDays: policy.AnnualDays,
-                isAnnualized: policy.IsAnnualized,
-                resetCarryInterest: 0m,
-                realizedInterest: 0m,
-                unwindFraction: 1m,
-                finalBasis: out finalBasis,
-                trace: trace,
-                carryInInterest: carryInInterest);
-            amount = r.Accrued;
-        }
-        else
-        {
-            // 单利：无并本金语义，冻结利率即单段全程
-            var r = SimpleInterestAccrual.AccruePeriod(
-                priorAccrued: 0m,
-                notional: closePrincipal,
-                unwindFraction: 1m,
-                segmentRates: new List<(DateTime StartDate, decimal Rate)> { (unwindDate, allInRate) },
-                startDate: unwindDate,
-                endDate: maturityDate,
-                priorValueDate: unwindDate.AddDays(-1),
-                boundary: boundary,
-                annualDays: policy.AnnualDays,
-                isAnnualized: policy.IsAnnualized,
-                trace: trace);
-            amount = r.Accrued;
-            finalBasis = closePrincipal;
-        }
+        // 按计息方式分派到对应的纯计息路径；二者均产出 (累计利息, 末段计息基数)。
+        // 计息数学细节下沉到具名方法，使本方法只表达“分派 + 组装事件”的编排意图，便于阅读与单测。
+        var (accrued, finalBasis) = policy.IsCompound
+            ? AccrueCompound(closePrincipal, capitalizedInterest, carryInInterest, unwindDate, maturityDate, boundary, policy, resetAnchor, allInRate, trace)
+            : AccrueSimple(closePrincipal, unwindDate, maturityDate, boundary, policy, allInRate, trace);
 
-        var rounded = InterestMath.Round(amount, InterestMath.FundingLegPrecision);
+        var rounded = InterestMath.Round(accrued, InterestMath.FundingLegPrecision);
         var interest = new swap_flow_event
         {
             SwapTradeId = td.id,
@@ -137,6 +100,58 @@ public static class SwapPenaltyInterestCalculator
         return interest;
     }
 
+    /// <summary>
+    /// 复利罚息计息：即使冻结利率为单值，也必须按重置日分段（并本金发生在分段边界），每段同一冻结利率。
+    /// notional = 本金 + 已并入最近重置日的利息（capitalizedInterest）：全期轨迹中当前重置段的滚动基数，
+    /// 段内每一天都在其上计息——平仓日落在段中间时与全期逐日对齐的关键。carryInInterest 在首个窗口重置日并入。
+    /// 返回 (累计利息, 末段计息基数)。
+    /// </summary>
+    private static (decimal Accrued, decimal FinalBasis) AccrueCompound(
+        decimal closePrincipal, decimal capitalizedInterest, decimal carryInInterest,
+        DateTime unwindDate, DateTime maturityDate, AccrualBoundary boundary, AccrualPolicy policy,
+        DateTime resetAnchor, decimal allInRate, AccrualTrace? trace)
+    {
+        var segments = BuildFrozenSegments(unwindDate, maturityDate, policy.ResetPeriodDays, resetAnchor, allInRate);
+        var r = CompoundInterestAccrual.AccruePeriod(
+            notional: closePrincipal + capitalizedInterest,
+            segmentRates: segments,
+            startDate: unwindDate,
+            endDate: maturityDate,
+            boundary: boundary,
+            annualDays: policy.AnnualDays,
+            isAnnualized: policy.IsAnnualized,
+            resetCarryInterest: 0m,
+            realizedInterest: 0m,
+            unwindFraction: 1m,
+            finalBasis: out var finalBasis,
+            trace: trace,
+            carryInInterest: carryInInterest);
+        return (r.Accrued, finalBasis);
+    }
+
+    /// <summary>
+    /// 单利罚息计息：无并本金语义，冻结利率即单段全程。finalBasis 恒为本金（单利不滚基数）。
+    /// 返回 (累计利息, 末段计息基数)。
+    /// </summary>
+    private static (decimal Accrued, decimal FinalBasis) AccrueSimple(
+        decimal closePrincipal, DateTime unwindDate, DateTime maturityDate,
+        AccrualBoundary boundary, AccrualPolicy policy, decimal allInRate, AccrualTrace? trace)
+    {
+        var r = SimpleInterestAccrual.AccruePeriod(
+            priorAccrued: 0m,
+            notional: closePrincipal,
+            unwindFraction: 1m,
+            segmentRates: new List<(DateTime StartDate, decimal Rate)> { (unwindDate, allInRate) },
+            startDate: unwindDate,
+            endDate: maturityDate,
+            priorValueDate: unwindDate.AddDays(-1),
+            boundary: boundary,
+            annualDays: policy.AnnualDays,
+            isAnnualized: policy.IsAnnualized,
+            trace: trace);
+        return (r.Accrued, closePrincipal);
+    }
+
     /// <summary>
     /// 复利冻结分段：段边界 = 窗口内重置日（(d - anchor) % period == 0，对齐 IsResetDay 公式），
     /// 每段填同一冻结利率。首段必为 (unwindDate, rate)；[start,end] 含端点的重置日也生成段