The settings slice of #35.
- A settings page (admins only) for description, website, topics, visibility, git:// exposure, the four merge gates, branch protection, and archiving. Every control dispatches the matching command.
- repo settings visibility is new: it had no command at all, so it lands over SSH first. Going private drops git:// exposure with it.
- Delete and transfer stay CLI-only, as does everything credential shaped.
e2e drives each control and verifies through repo show and settings show, including a private repo disappearing from anonymous surfaces and a rejected website URL surfacing the command's message.
Ref #35