Function mintExactCost

Mint a lot-rounded position within an all-in max_cost budget.

Unlike mint_exact_amount, fees are sized inside the budget: the quantity search evaluates the all-in withdrawal the mint charges (premium + trader-paid fee + builder_fee + EWMA penalty + inventory_impact_charge) against the fee-incentive, congestion, and book state at execution, so the debit never exceeds max_cost. max_cost is first capped to the account's available USDC after settlement, so std::u64::max_value!() sizes against the whole balance.

The budget search finds the largest fitting quantity. If that quantity costs more than its maximum payout, a conservative search tries a smaller fill; rounding can make that fallback miss a larger admissible fill. Only when the budget is the limiting constraint is the remainder less than the incremental all-in cost of one more lot. Payout-limited fills and lot-cap saturation can leave more. Insufficient expiry cash backing aborts the mint; sizing does not shrink the fill to available backing, and the quote does not preflight it.

min_quantity is this entrypoint's slippage guard. The budget is fixed, so every adverse move between building the transaction and executing it — the price, the congestion surcharge, the sponsor subsidy, the inventory-impact charge — shows up as fewer contracts, and a fill below min_quantity aborts EMintQuantityBelowMin. It bounds the all-in price per contract at max_cost / min_quantity, which is why the shape carries no separate probability cap; passing 0 accepts any fill the budget buys. A budget too small to admit constants::min_premium aborts EPremiumBelowMinimum rather than minting nothing, and zero is such a budget: unlike mint_exact_amount there is no max_cost cap to require, because here the budget IS the sizing input. Other requirements match mint_exact_quantity. Returns the minted order ID.