单笔期权默认改为币本位；未配置时按coin处理

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

lib/options/options_margin_mode_lib.py

@@ -24,13 +24,18 @@ def _env_float(name: str, default: float) -> float:
 
 
 def normalize_options_margin_mode(raw: Any = None) -> str:
-    """返回 usdc | coin."""
+    """返回 usdc | coin;未配置时默认币本位."""
     if raw is None:
         raw = os.getenv("OKX_OPTIONS_MARGIN_MODE")
-    v = str(raw or MODE_USDC).strip().lower()
+    v = str(raw or MODE_COIN).strip().lower()
+    if v in ("usdc", "usdc_margin", "usd_margin", "u本位", "u"):
+        return MODE_USDC
     if v in ("coin", "coin_margin", "crypto", "crypto_margin", "币本位"):
         return MODE_COIN
-    return MODE_USDC
+    # 空串或未知值:默认币本位
+    if not v:
+        return MODE_COIN
+    return MODE_COIN
 
 
 def is_coin_margin_mode(raw: Any = None) -> bool: