[POS] Products that are not available for POS, can be added to cart via POS Extensions Cart API

[xqwtsz]

Please list the package(s) involved in the issue, and include the version you are using

"@shopify/ui-extensions": "2024.10.x",
"@shopify/ui-extensions-react": "2024.10.x"

Describe the bug

Products that are not available for POS Sales Channel, can still be added to cart via POS Extensions Cart API, which does occasionally show a cart error with no extra information (just a generic "something is wrong with the cart"), but the product is still added to cart and the checkout can be completed.

Steps to reproduce the behavior:

1. Create a fresh POS UI Extension
2. Run the api.cart.addLineItem function with a product that is not in the POS Sales Channel

const api = useApi<'pos.home.modal.render'>()
await api.cart.addLineItem("productId", 1)

Expected behavior

Product that is not available in the POS sales channel is NOT added to the cart, with a proper error message.