Transferred from microsoft/vscode-copilot#18184

• We have "Add selection to chat", let's consider a keybinding (I think it could be a common interaction and a Cursor user at the conference believed that this was not possible in vscode)
• Clean up # menu- move 3 latest files to top?
  • How do we feel about nested entires in #, to match the "Add context" picker?
• "Open Editors" should not be at the top of the "add context" picker, it could be the 3 most recent files. And "Open Editors" should possibly not exist at all