Add forced_chatgpt_workspace_id and forced_login_method configuration options (#5303)

This PR adds support for configs to specify a forced login method
(chatgpt or api) as well as a forced chatgpt account id. This lets
enterprises uses [managed
configs](https://developers.openai.com/codex/security#managed-configuration)
to force all employees to use their company's workspace instead of their
own or any other.

When a workspace id is set, a query param is sent to the login flow
which auto-selects the given workspace or errors if the user isn't a
member of it.

This PR is large but a large % of it is tests, wiring, and required
formatting changes.

API login with chatgpt forced
<img width="1592" height="116" alt="CleanShot 2025-10-19 at 22 40 04"
src="https://github.com/user-attachments/assets/560c6bb4-a20a-4a37-95af-93df39d057dd"
/>

ChatGPT login with api forced
<img width="1018" height="100" alt="CleanShot 2025-10-19 at 22 40 29"
src="https://github.com/user-attachments/assets/d010bbbb-9c8d-4227-9eda-e55bf043b4af"
/>

Onboarding with api forced
<img width="892" height="460" alt="CleanShot 2025-10-19 at 22 41 02"
src="https://github.com/user-attachments/assets/cc0ed45c-b257-4d62-a32e-6ca7514b5edd"
/>

Onboarding with ChatGPT forced
<img width="1154" height="426" alt="CleanShot 2025-10-19 at 22 41 27"
src="https://github.com/user-attachments/assets/41c41417-dc68-4bb4-b3e7-3b7769f7e6a1"
/>

Logging in with the wrong workspace
<img width="2222" height="84" alt="CleanShot 2025-10-19 at 22 42 31"
src="https://github.com/user-attachments/assets/0ff4222c-f626-4dd3-b035-0b7fe998a046"
/>

codex-rs/login/src/device_code_auth.rs

@@ -186,6 +186,13 @@ pub async fn run_device_code_login(opts: ServerOptions) -> std::io::Result<()> {
     .await
     .map_err(|err| std::io::Error::other(format!("device code exchange failed: {err}")))?;
 
+    if let Err(message) = crate::server::ensure_workspace_allowed(
+        opts.forced_chatgpt_workspace_id.as_deref(),
+        &tokens.id_token,
+    ) {
+        return Err(io::Error::new(io::ErrorKind::PermissionDenied, message));
+    }
+
     crate::server::persist_tokens_async(
         &opts.codex_home,
         None,