Add note about ChatRequest#model

Author: roblourens

release-notes/v1_95.md

@@ -398,6 +398,14 @@ Welcome views now support the ability to render codicons. You can do so using th
 
 ![a sample welcome view showing the use of text, links, buttons, and codicons](images/1_95/welcome-view-codicons.png)
 
+### Chat participant access to model picker
+
+You may have noticed the model picker in the chat view, which allows you to select the model used for a chat request.
+
+![Copilot model picker control in the Chat view enables switching to another language model.](./images/1_94/copilot-model-picker.png)
+
+Your chat participant extension needs to adopt a new API in order to use this. We just finalized a new `model` property on the `ChatRequest` object, which will be set to the `LanguageModelChat` instance for the model in the picker. You can use this instead of the `lm.selectChatModels` method. If your extension wants to use a particular model besides the selected one, you can still use `lm.selectChatModels` instead.
+
 ## Preview Features
 
 ### TypeScript 5.7