[App] Allow Cloud repositories to be removed from the sidebar

What variant of Codex are you using?

Codex App on macOS, version 26.715.61943 (build 5628)

What feature would you like to see?

Cloud repositories cannot currently be removed or hidden from the Codex App sidebar.

Local projects have a three-dot menu with project actions. Cloud repositories only has the new-chat button and no three-dot menu.

Please add a Remove from sidebar or Hide from sidebar action for Cloud repositories.

This action should only remove the repository group from the sidebar. It should not delete the GitHub repository or its existing Cloud chats.

Additional information

Here are two screenshots, the first one is of a regular local project, the second one is a cloud project. The first screenshot shows a local project with a three-dot menu. The second screenshot shows a Cloud repository without that menu.

<img width="256" height="33" alt="Image" src="https://github.com/user-attachments/assets/20935131-8b57-4988-90b9-43cc6dc0c579" />
<img width="274" height="45" alt="Image" src="https://github.com/user-attachments/assets/52f3d8c8-9a5e-412d-a2fc-12cb747cce57" />