sidebar of vscode: Ask Copilot. it's a chat interface. right clicking the tab icon, shows buttons such as "Hide Chat" and separately a checkbox to enable/disable the "Chat" pane. Both are disabled and unclickable. There is no X button to close this. The context menu does have an option to hide the entire secondary sidebar, but not to remove just the Chat tab from it.
https://gaysex.cloud/files/5c65c5ea-a3bc-4b4a-929b-f9bcdd960e76.png