Fix coin-margin expiry breakeven to use coin premium formula.

Use K/(1-p) and K/(1+p) for coin calls/puts instead of adding ETH premium to USD strike; align T-view straddle band with coin quotes.

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

lib/exchange/okx_options_lib.py

@@ -889,6 +889,7 @@ def build_option_chain(
             strike=strike,
             ask_px=ask,
             mark_px=mark,
+            quote_in_coin="_UM" not in (family or "").upper(),
         )
         mny = option_moneyness(opt_type=opt_type, strike=strike, index_px=idx)
         exp_key = str(exp_ms)
@@ -1028,11 +1029,18 @@ def quote_option_contract(ex: ccxt.okx, inst_id: str) -> dict[str, Any]:
         idx = fetch_index_price(ex, uly)
         opt_type = meta.get("optType")
         strike = _safe_float(meta.get("stk"))
+        try:
+            from lib.options.options_margin_mode_lib import margin_mode_from_inst_id
+
+            quote_in_coin = margin_mode_from_inst_id(inst_id) == "coin"
+        except Exception:
+            quote_in_coin = "USD_UM" not in inst_id.upper() and "-USD-" in inst_id.upper()
         expiry_be = expiry_breakeven_from_ask(
             opt_type=str(opt_type or ""),
             strike=strike,
             ask_px=book_ask if can_open else None,
             mark_px=mark,
+            quote_in_coin=quote_in_coin,
         )
         return {
             "ok": True,
@@ -1824,11 +1832,18 @@ def format_position_row(
         round(total_premium(avg, eth_amount), 8) if avg is not None and eth_amount > 0 else None
     )
     delta_pa = _safe_float(pos.get("deltaPA"))
+    try:
+        from lib.options.options_margin_mode_lib import margin_mode_from_inst_id
+
+        quote_in_coin = margin_mode_from_inst_id(inst_id) == "coin"
+    except Exception:
+        quote_in_coin = "USD_UM" not in inst_id.upper() and "-USD-" in inst_id.upper()
     expiry_be = expiry_breakeven_px(
         opt_type=str(opt_type or ""),
         strike=strike,
         avg_px=avg,
         be_px_api=_safe_float(pos.get("bePx")),
+        quote_in_coin=quote_in_coin,
     )
     close_be = close_breakeven_idx(
         opt_type=str(opt_type or ""),