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/protocol/src/error.rs

@@ -719,8 +719,9 @@ impl std::fmt::Display for UsageLimitReachedError {
                 "You've hit your usage limit. Visit https://chatgpt.com/codex/settings/usage to purchase more credits{}",
                 retry_suffix_after_or(self.resets_at.as_ref())
             ),
-            Some(PlanType::Known(KnownPlan::Enterprise))
-            | Some(PlanType::Known(KnownPlan::Edu)) => format!(
+            Some(PlanType::Known(
+                KnownPlan::Enterprise | KnownPlan::Edu | KnownPlan::EduPlus | KnownPlan::EduPro,
+            )) => format!(
                 "You've hit your usage limit.{}",
                 retry_suffix(self.resets_at.as_ref())
             ),