Allow EDU accounts to fetch cloud config bundles (#25963)

## Summary

Allow EDU ChatGPT workspaces to fetch cloud config bundles. The existing
cloud config eligibility gate only allowed business-like and enterprise
plans, which meant EDU admins could configure managed policies in the UI
but the Codex client would skip fetching them.

This keeps individual/pro and team-like usage-based plans excluded, and
adds service-level coverage for both `edu` and `education` plan aliases.

## Validation

- `just fmt`
- `just test -p codex-cloud-config`
- Built the Codex app locally, created a new EDU ChatGPT workspace, and
verified config bundles can be fetched and are properly applied.

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

@@ -49,7 +49,8 @@ fn cloud_config_eligible_auth(auth: &CodexAuth) -> bool {
         return false;
     };
     auth.uses_codex_backend()
-        && (plan_type.is_business_like() || matches!(plan_type, PlanType::Enterprise))
+        && (plan_type.is_business_like()
+            || matches!(plan_type, PlanType::Enterprise | PlanType::Edu))
 }
 
 fn optional_bundle(bundle: CloudConfigBundle) -> Option<CloudConfigBundle> {