Fix btc_eth live card option premium USDT conversion.

Use option (BTC) index for coin-to-U; never fall back to ETH perp mark. Also add no-server-ops Cursor rule.

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

tests/test_hedge_po_mode.py

@@ -172,6 +172,48 @@ class TestHedgePoMode(unittest.TestCase):
             self.assertEqual(p["exit_mode"], "profit")
             self.assertIn("子账户", p["instance_rule"])
 
+    def test_resolve_option_index_cross_no_perp_fallback(self):
+        # 跨币缺指数时不得用 ETH 永续价折 BTC 权利金(曾导致 0.014×2476≈34U)
+        from lib.hedge_plan.hedge_plan_live_positions_lib import resolve_option_index_px
+
+        with patch(
+            "lib.exchange.okx_public_http_lib.fetch_index_px",
+            side_effect=RuntimeError("no net"),
+        ):
+            px = resolve_option_index_px(
+                {},
+                "BTC",
+                ex_opt=None,
+                cross_asset=True,
+                perp_fallback=2476.0,
+            )
+            self.assertIsNone(px)
+
+        with patch(
+            "lib.exchange.okx_public_http_lib.fetch_index_px",
+            return_value=91000.0,
+        ):
+            px = resolve_option_index_px(
+                {},
+                "BTC",
+                cross_asset=True,
+                perp_fallback=2476.0,
+            )
+            self.assertAlmostEqual(px, 91000.0)
+
+        # 同币允许永续价兜底
+        with patch(
+            "lib.exchange.okx_public_http_lib.fetch_index_px",
+            side_effect=RuntimeError("no net"),
+        ):
+            px = resolve_option_index_px(
+                {},
+                "ETH",
+                cross_asset=False,
+                perp_fallback=2476.0,
+            )
+            self.assertAlmostEqual(px, 2476.0)
+
 
 if __name__ == "__main__":
     unittest.main()