- CargoHold gains a parallel `costs` ledger (credits/unit actually paid, or null when no cost is on file), kept aligned across add/remove/set/capacity/dropFirstNot and serialized via toJSON/fromJSON
- ShopView stamps each bought bay with the trade's unit price so the console can compare exit prices against what was really paid
- ShipScreenModel/ShipWindow surface per-bay costs, a total-cost hold meta line, and a "PAID" chip + reference line in the bay manifest; bays with no cost read "NO COST" instead of inventing one
- GameScene passes the bay's recorded cost into scoutGood() so exit profits re-baseline against the purchase (falling back to the catalog value when absent), and restore/quest-handoff paths load null costs cleanly for legacy saves
- Adds arid-shop-02 video asset and updates cargo/saves/ship-window/shop-ui tests to cover the new ledger
