fix(swap): 修复复利重置日部分平仓后本金计算逻辑

- 修复复利重置日部分平仓后当日利息计算，使用已结转待实现利息的剩余复利本金
- 修复算尾部分平仓后EOD保留剩余复利本金的逻辑，按计息模式返回口径处理
- 修复模式2和模式9在部分平仓时的本金计算差异，避免重复比例调整
- 修复不算尾情况下重置日后已并入本金的待实现利息遗漏问题
- 新增对话案例回归测试验证部分平仓后最终全平场景的正确性
- 添加多种计息模式和交易类型的回归测试用例

UnitTestProject/Modules/SwapModule/DealInterestsScenarioTest.cs

@@ -837,6 +837,8 @@ namespace YLErp.Modules.SwapModule
 
             AssertDecimal(compoundPrincipalAfterSevenDays, result.TdInterestPrincipal,
                 "复利重置日部分平仓后，EOD 本金必须保留 CalcSwapInterests 计算的 7 天复利本金");
+            AssertDecimal(compoundPrincipalAfterSevenDays * FixedRate / AnnualDays, result.TdInterestIncome,
+                "复利重置日部分平仓后，当日利息必须使用已结转待实现利息的剩余复利本金");
         }
 
         [TestMethod]
@@ -901,6 +903,42 @@ namespace YLErp.Modules.SwapModule
                 "算尾部分平仓：InterestIncomeSum 应=前日待实现+当日新计(含被平仓部分)-当日实现");
         }
 
+        [DataTestMethod]
+        [DataRow((int)InterestModeEnum.合约名义本金规模, "300")]
+        [DataRow((int)InterestModeEnum.标的期初全价, "700")]
+        public void DI_GLMS_20260421_0004_CalcLastKeepsRemainingCompoundPrincipal(
+            int interestMode, string calculatedPrincipalText)
+        {
+            var service = new StubEodPositionService
+            {
+                AutoInterests = new List<swap_flow_event>
+                {
+                    new() { InterestPrincipal = decimal.Parse(calculatedPrincipalText) }
+                }
+            };
+            var td = CreateTrade();
+            td.trade_extend.ExtendJson = JsonConvert.SerializeObject(new TradeExtendJson
+            {
+                AnnualDays = AnnualDays,
+                InterestCalcMode = "11",
+                SettlementRules = 1
+            });
+            var position = CreateInterestPosition();
+            position.InterestMode = interestMode;
+            position.InterestType = (int)InterestTypeEnum.复利;
+            var previousEod = CreatePreEod(StartDate.AddDays(2), 100m);
+            previousEod.TdInterestPrincipal = Principal;
+            var closeFlow = CreateSwapFlowEvent(StartDate.AddDays(3), 50m);
+            closeFlow.EventType = (int)SwapFlowEventTypeEnum.平仓;
+
+            var result = service.ExecuteSaveAutoEodWithCloseInterestPosition(
+                previousEod, position, td, StartDate.AddDays(3), null,
+                700m, 0m, new List<swap_flow_event> { closeFlow }, 300m, false);
+
+            AssertDecimal(700m, result.TdInterestPrincipal,
+                "算尾部分平仓后，EOD 必须按计息模式的返回口径保留剩余70%复利本金");
+        }
+
         [TestMethod]
         public void DI_MANUAL_PARTIAL_CLOSE_NoCalcLastUsesRemainingPrincipalDailyInterest()
         {