feat: [#1] type full api surface and add delivery-areas & marketplace

[xedosystems]

Summary

Regenerate the SDK types from the updated Developer API v1 spec — every entity is
now precisely typed instead of an open JsonObject — and expose the two new
read endpoints (delivery-areas, marketplace).

Changes

• Refreshed the vendored openapi.json and regenerated src/types/generated.ts
• Rewrote src/types/public.ts to derive all entity, enum and input types from
  generated.ts (stays in sync on every npm run generate)
• Added named enums: OrderStatus, CartStatus, FulfillmentStatus,
  DeliveryType, PaymentStatus, OrderPaymentMethod, PriceAdjustmentType,
  MediaType
• Split list vs detail shapes: list()/listAll() now return OrderListItem /
  CartListItem, retrieve() returns the full Order / Cart
• Overrode meta back to JsonObject (openapi-typescript emits the useless
  Record<string, never>)
• Added Carts.pay() return type CheckoutRetryResult; createAndPay() now
  returns CheckoutResult | CheckoutRetryResult
• Added DeliveryAreas and Marketplace resources, wired into the Xedo client
• Updated exports in src/index.ts, the README resource table and the example

API

Endpoint: GET /v1/delivery-areas

Returns DeliveryArea[] — { id, name, deliveryCost }. Use id as
delivery.deliveryAreaId when creating a cart.

Endpoint: GET /v1/marketplace

Returns the MarketplaceProfile (payment config, split-payment settings,
business category, …).

Access: Bearer xdk_… developer API key