Move auth code into login crate (#15150)

- Move the auth implementation and token data into codex-login.
- Keep codex-core re-exporting that surface from codex-login for
existing callers.

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/tui/src/status/helpers.rs

@@ -92,7 +92,7 @@ pub(crate) fn compose_account_display(
 
     match auth.auth_mode() {
         CoreAuthMode::ApiKey => Some(StatusAccountDisplay::ApiKey),
-        CoreAuthMode::Chatgpt => {
+        CoreAuthMode::Chatgpt | CoreAuthMode::ChatgptAuthTokens => {
             let email = auth.get_account_email();
             let plan = plan
                 .map(|plan_type| title_case(format!("{plan_type:?}").as_str()))