fix复盘真盈亏按权利金USDT波动公式计算，忽略现货多买。

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_options_pnl_settle.py

@@ -7,6 +7,7 @@ from lib.options.options_pnl_settle_lib import (
     fee_to_premium_ccy,
     settle_closed_pnl,
     settle_exchange_realized_pnl,
+    true_pnl_usdt_premium_move,
 )
 from lib.options.options_stats_lib import (
     apply_exchange_pnl_freeze,
@@ -24,6 +25,26 @@ class FeeConvertTests(unittest.TestCase):
         )
 
 
+class PremiumMoveFormulaTests(unittest.TestCase):
+    def test_user_formula_matches_proceeds_minus_open_cost(self):
+        coin = 0.01
+        paid = 0.01
+        open_px = 90000.0
+        close_px = 80000.0
+        a = true_pnl_usdt_premium_move(
+            coin_pnl=coin,
+            premium_paid=paid,
+            open_index_px=open_px,
+            sell_back_px=close_px,
+        )
+        # 历史盈亏×卖回 − (权利金×开 − 权利金×平)
+        expect = coin * close_px - (paid * open_px - paid * close_px)
+        self.assertAlmostEqual(float(a), expect, places=4)
+        # 无费时 ≡ 收回×平 − 已付×开 (recv=paid+coin)
+        recv = paid + coin
+        self.assertAlmostEqual(float(a), recv * close_px - paid * open_px, places=4)
+
+
 class SettleClosedPnlTests(unittest.TestCase):
     def test_sim_net_times_close_index(self):
         # 无开仓指数时回退净币×平仓价