Add pre-buy expiry breakeven columns to options chain table.

Show estimated expiry balance and distance from index in the chain list and order panel using ask price before opening a position.

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

lib/options/options_pricing_lib.py

@@ -134,6 +134,18 @@ def option_moneyness_label(moneyness: str) -> str:
     return {"itm": "实值", "otm": "虚值", "atm": "平值"}.get((moneyness or "").lower(), "")
 
 
+def expiry_breakeven_from_ask(
+    *,
+    opt_type: str,
+    strike: float | None,
+    ask_px: float | None,
+    mark_px: float | None = None,
+) -> float | None:
+    """买入前预估到期平衡：权利金按卖一；无卖一时回退标记价。"""
+    prem = ask_px if ask_px is not None and ask_px > 0 else mark_px
+    return expiry_breakeven_px(opt_type=opt_type, strike=strike, avg_px=prem)
+
+
 def expiry_breakeven_px(
     *,
     opt_type: str,