fix: validate historical trade chain changes

tests/test_services.py

@@ -129,3 +129,51 @@ def test_service_validates_lot_size_and_available_sell_quantity(tmp_path):
     )
 
     assert saved_sell.id is not None
+
+
+def test_service_rejects_historical_changes_that_break_future_sells(tmp_path):
+    service = TradingService(tmp_path / "grid.db")
+    service.ensure_defaults()
+    account = service.get_active_account()
+    instrument = service.add_instrument(Instrument(id=None, code="159915", name="创业板ETF"))
+    buy = service.save_trade(
+        Trade(
+            id=None,
+            account_id=account.id,
+            instrument_id=instrument.id,
+            trade_date=date(2026, 7, 7),
+            side=TradeSide.BUY,
+            price=Decimal("2.00"),
+            quantity=200,
+            trade_group=TradeGroup.GRID,
+        )
+    )
+    service.save_trade(
+        Trade(
+            id=None,
+            account_id=account.id,
+            instrument_id=instrument.id,
+            trade_date=date(2026, 7, 8),
+            side=TradeSide.SELL,
+            price=Decimal("2.10"),
+            quantity=200,
+            trade_group=TradeGroup.GRID,
+        )
+    )
+
+    with pytest.raises(ValueError, match="后续成交"):
+        service.update_trade(
+            Trade(
+                id=buy.id,
+                account_id=account.id,
+                instrument_id=instrument.id,
+                trade_date=date(2026, 7, 7),
+                side=TradeSide.BUY,
+                price=Decimal("2.00"),
+                quantity=100,
+                trade_group=TradeGroup.GRID,
+            )
+        )
+
+    with pytest.raises(ValueError, match="后续成交"):
+        service.delete_trade(buy.id)