Fix false USDC-short error while waiting for a qualified option.

Use risk-sizing preview ask/qty (same as auto-convert) instead of monitor book ask.

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

backend/app/strategy/auto_usdc.py

@@ -44,7 +44,9 @@ def _round_down(n: float, nd: int = 2) -> float:
 
 def preview_capacity_for_convert(db: Database | None = None) -> dict[str, Any]:
     """
-    用盘口预览以损定仓名义评估资金门（不写 settings）。
+    用预览以损定仓名义评估资金门（不写 settings）。
+    - 选约杠杆：用定仓卖一（指数/杠杆下限），与预算/k 一致，勿用监控未达标贵卖一
+    - 实际杠杆：用盘口卖一
     手动仓位则直接 assess 当前账本名义。
     """
     database = db or get_db()
@@ -53,7 +55,8 @@ def preview_capacity_for_convert(db: Database | None = None) -> dict[str, Any]:
 
         prev = preview_risk_sizing(database)
         if prev.get("risk_based") and prev.get("ok"):
-            return assess_open_capacity(
+            # option_ask 在 preview 里已是定仓口径（selection=隐含 / actual=盘口）
+            cap = assess_open_capacity(
                 database,
                 option_ask=float(prev["option_ask"])
                 if prev.get("option_ask") is not None
@@ -64,10 +67,21 @@ def preview_capacity_for_convert(db: Database | None = None) -> dict[str, Any]:
                 perp_qty_eth=float(prev["perp_qty_eth"])
                 if prev.get("perp_qty_eth") is not None
                 else None,
+                call_ask=float(prev["call_ask"])
+                if prev.get("call_ask") is not None
+                else None,
+                put_ask=float(prev["put_ask"])
+                if prev.get("put_ask") is not None
+                else None,
             )
+            cap["capacity_basis"] = "risk_preview"
+            cap["leverage_basis"] = prev.get("leverage_basis")
+            return cap
     except Exception:
         logger.exception("preview capacity for convert failed")
-    return assess_open_capacity(database)
+    cap = assess_open_capacity(database)
+    cap["capacity_basis"] = "ledger"
+    return cap
 
 
 def prepare_okx_trading_usdc(db: Database | None = None) -> dict[str, Any]: