Fix swap-all balance by reading OKX funding via asset/balances API.

Swap-all targets funding account but ccxt free was often empty; fall back to trading USDT for unified accounts and show balances in errors.

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

tests/test_okx_funding_balances.py

@@ -0,0 +1,39 @@
+"""OKX 资金账户余额(asset/balances)."""
+from __future__ import annotations
+
+import unittest
+from unittest.mock import MagicMock
+
+from lib.exchange.okx_options_lib import (
+    fetch_funding_balances_via_asset_api,
+    fetch_options_balances,
+)
+
+
+class TestOkxFundingBalances(unittest.TestCase):
+    def test_asset_balances_parsed(self):
+        ex = MagicMock()
+        ex.private_get_asset_balances.return_value = {
+            "data": [
+                {"ccy": "USDT", "availBal": "25.5", "bal": "30"},
+                {"ccy": "USDC", "availBal": "10", "bal": "10"},
+            ]
+        }
+        total, avail = fetch_funding_balances_via_asset_api(ex)
+        self.assertEqual(avail["USDT"], 25.5)
+        self.assertEqual(total["USDT"], 30.0)
+        self.assertEqual(avail["USDC"], 10.0)
+
+    def test_fetch_options_balances_merges_asset_api(self):
+        ex = MagicMock()
+        ex.fetch_balance.return_value = {"free": {}, "total": {}}
+        ex.private_get_asset_balances.return_value = {
+            "data": [{"ccy": "USDT", "availBal": "18.2", "bal": "18.2"}]
+        }
+        bal = fetch_options_balances(ex, force=True)
+        self.assertEqual(bal["funding_usdt_avail"], 18.2)
+        self.assertEqual(bal["funding_usdt"], 18.2)
+
+
+if __name__ == "__main__":
+    unittest.main()