Support Edu Plus and Edu Pro account plans (#39316)

## What changed

- Recognize `edu_plus` and `edu_pro` as distinct education workspace plans across authentication, backend rate-limit mapping, and app-server account schemas.
- Include both plans in cloud configuration eligibility and use the education usage-limit behavior.
- Display the plans as `Edu Plus` and `Edu Pro` in the TUI status view.

## Testing

- Cover parsing, workspace classification, account and rate-limit responses, cloud configuration eligibility, usage-limit messages, and TUI display names for the new variants.

GitOrigin-RevId: bf8add780ae03a3c6d10c4f4afa0da262c37928e

codex-rs/cloud-config/src/service.rs

@@ -51,7 +51,8 @@ fn cloud_config_eligible_auth(auth: &CodexAuth) -> bool {
     };
     auth.uses_codex_backend()
         && (plan_type.is_business_like()
-            || matches!(plan_type, PlanType::Enterprise | PlanType::Edu))
+            || plan_type.is_education_like()
+            || plan_type == PlanType::Enterprise)
 }
 
 fn optional_bundle(bundle: CloudConfigBundle) -> Option<CloudConfigBundle> {