cherry-pick(#37758): docs: mention VS Code insiders in the agents docs

Author: pavelfeldman

docs/src/test-agents-js.md

@@ -43,6 +43,10 @@ npx playwright init-agents --loop=claude
 npx playwright init-agents --loop=opencode
 ```
 
+:::note
+VS Code v1.105 (currently on the [VS Code Insiders channel](https://code.visualstudio.com/insiders/)) is needed for the agentic experience in VS Code. It will become stable shortly, we are a bit ahead of the curve with this functionality!
+:::
+
 Once the agents have been generated, you can use your AI tool of choice to command these agents to build Playwright Tests.