Enrich JSDoc for Checkout APIs property descriptions, 2025-10

[rennyG]

Partially closes https://github.com/shop/issues-learn/issues/1047

Summary

• Ports enriched JSDoc descriptions from checkout-web (shop/world#548830) to ui-extensions 2025-10
• Covers all 16 Checkout APIs across 10 files: shared types, StandardApi, CheckoutApi, OrderConfirmationApi, CartLineItemApi, ShippingOptionItemApi, ShippingOptionListApi, PickupLocationItemApi, PickupLocationListApi, PickupPointListApi
• Preserves 2025-10-specific types (MetafieldRemoveChange, MetafieldUpdateChange) with appropriate JSDoc
• Every description verified against the 2025-10 TypeScript types
• Follows Shopify style guide: contractions, no Latinisms, present tense, colon bullet format for enums

Test plan

• yarn tsc --noEmit passes
• yarn docs:checkout 2025-10 generates successfully
• Verify enriched descriptions appear correctly in shopify-dev docs preview

🤖 Generated with Claude Code

[github-actions]

🚨🚨🚨 Docs migration in progress 🚨🚨🚨

We are actively migrating UI extension reference docs to MDX in the areas/platforms/shopify-dev zone of the monorepo. This impacts docs for the following surfaces:

• Admin UI extensions
• App Home
• Checkout UI extensions
• Customer account UI extensions
• POS UI extensions

During this migration, please be aware of the following:

.doc.ts files are being deprecated. Changes to .doc.ts files in this repo will not be reflected in the new MDX-based docs. If you need to update docs for a reference that has already been migrated, make your changes directly in the areas/platforms/shopify-dev zone of the monorepo instead.

Doc comments in .ts source files (the comment blocks above types and functions) are also affected. Generating docs from these comments currently requires a newer version of the @shopify/generate-docs library that isn't yet available. Updates to doc comments may not produce the expected output until the migration is complete.

Examples that previously lived in this repo are being moved to the areas/platforms/shopify-dev zone of the monorepo and should be authored there going forward.

What should I do?

• If your PR includes changes to .doc.ts files, doc comments, or examples, please reach out to us in #devtools-proj-templated-refs so we can help ensure your updates are captured correctly.
• If your PR is limited to source code changes (non-docs), you can ignore this notice.

Thanks for your patience while we complete the migration! 🙏