update root readme based on remote-dom updates (#3505)

Author: lrsterrett

README.md

@@ -2,19 +2,16 @@
 
 This repo contains the public definition of Shopify’s UI extension API. App developers can use these libraries for a strongly-typed, optimized development experience that lets them focus on integrating their app’s features deep into Shopify workflows. You can learn more about what is possible with UI extensions in [Shopify’s developer documentation](https://shopify.dev/api/checkout-extensions/checkout).
 
-> **Note:** UI extensions are a [versioned API](https://shopify.dev/api/usage/versioning). This branch contains the APIs for the `unstable` API version. The following API versions are available as separate branches in this repo: [`2023-04`](https://github.com/Shopify/ui-extensions/tree/2023-04), [`2023-07`](https://github.com/Shopify/ui-extensions/tree/2023-07)
+> **Note:** UI extensions are a [versioned API](https://shopify.dev/api/usage/versioning). This branch contains the APIs for the `2025-10` API version. The following API versions are available as separate branches in this repo: [`2023-04`](https://github.com/Shopify/ui-extensions/tree/2023-04), [`2023-07`](https://github.com/Shopify/ui-extensions/tree/2023-07)
 
-Shopify provides different “variants” of UI extension APIs that are suitable for different developers:
-
-- [`@shopify/ui-extensions`](./packages/ui-extensions/) lets developers use a small, strongly-typed JavaScript API for creating UI extensions
-- [`@shopify/ui-extensions-react`](./packages/ui-extensions-react/) lets developers create UI extensions using [React](https://reactjs.org/), a popular JavaScript library for building user interfaces
+Shopify provides UI extension APIs via the [`@shopify/ui-extensions` package](./packages/ui-extensions/) which lets developers use a small, strongly-typed JavaScript API for creating UI extensions
 
 ## What are “UI extensions”?
 
 A UI extension is a JavaScript-based module that can hook in to client-side behaviors on any of Shopify’s first party UI surface areas. The most minimal definition of a UI extension has the following properties, which are configured in a `shopify.extension.toml` file in your project:
 
 - A `name` that is presented to merchants when interacting with the extension.
-- The [`target`](https://shopify.dev/docs/apps/app-extensions/configuration#targets) that the UI extension wishes to inject into. These are represented with string identifiers that describe the surface and responsibility of the extension. For example, [`purchase.checkout.cart-line-item.render-after` target](https://shopify.dev/docs/api/checkout-ui-extensions/unstable/apis/extensiontargets) gives a UI Extension the ability to render UI after the each cart line in a checkout.
+- The [`target`](https://shopify.dev/docs/apps/app-extensions/configuration#targets) that the UI extension wishes to inject into. These are represented with string identifiers that describe the surface and responsibility of the extension. For example, [`purchase.checkout.cart-line-item.render-after` target](https://shopify.dev/docs/api/checkout-ui-extensions/latest/targets) gives a UI Extension the ability to render UI after the each cart line in a checkout.
 - The JavaScript `module` in your local project that will be run to render UI.
 
 The types in this package allow us to represent additional details about the targets developers can implement. Each target can have a custom set of APIs available to it, which includes:
@@ -23,3 +20,5 @@ The types in this package allow us to represent additional details about the tar
 - What **imperative APIs** are provided by the host application, for reading and writing data relevant to the extension
 
 UI extensions are built on an open source project called, [remote-dom](https://github.com/Shopify/remote-dom), which allows them to render native UI elements while being safely sandboxed.
+
+> **Note:** If you are migrating from an API version prior to `2025-10`, you can follow the [migration guide](https://shopify.dev/docs/api/checkout-ui-extensions/2025-10/upgrading-to-2025-10).

packages/ui-extensions/README.md

@@ -6,6 +6,8 @@ This package supports the development of UI extension for [Admin](https://shopif
 
 All extensions, regardless of where they appear in Shopify, make use of the same [underlying technology](https://github.com/Shopify/remote-dom), and most of the same “core” components (e.g., `s-block`, `s-button`, `s-text-field`, etc) and capabilities (e.g., direct API access, session tokens). Separating APIs by surface makes it easier for a developer to see what is available to them in each context, and gives us a flexible system for introducing components and APIs available in only some areas of Shopify.
 
+> **Note:** If you are migrating from an API version prior to `2025-10`, you can follow the [migration guide](https://shopify.dev/docs/api/checkout-ui-extensions/2025-10/upgrading-to-2025-10).
+
 A checkout extension using Preact would be written as follows:
 
 ```ts