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/cli/src/login.rs

@@ -328,7 +328,7 @@ pub async fn run_login_status(cli_config_overrides: CliConfigOverrides) -> ! {
                     std::process::exit(1);
                 }
             },
-            AuthMode::Chatgpt => {
+            AuthMode::Chatgpt | AuthMode::ChatgptAuthTokens => {
                 eprintln!("Logged in using ChatGPT");
                 std::process::exit(0);
             }