Extend rate limit reads with usage capabilities (#42358)

## What changed

- Accept optional `account/rateLimits/read` capabilities for Luna Reserve support
  and lightweight background polling while preserving omitted and `null` params.
- Forward the Luna Reserve capability only for eligible ChatGPT sessions, and let
  lightweight polls skip the separate reset-credit detail request.
- Return the backend's `ordinaryUsageAllowed` decision only when its account and
  user identity match the active session.

## Testing

- Cover capability defaults, eligible and restricted authentication modes,
  lightweight polling, identity filtering, and backend permission handling.

GitOrigin-RevId: f407a3ae1e70e411fdf245f072a16e453f59cd87

codex-rs/app-server/src/message_processor.rs

@@ -1592,8 +1592,8 @@ impl MessageProcessor {
             ClientRequest::GetAuthStatus { params, .. } => {
                 self.account_processor.get_auth_status(params).await
             }
-            ClientRequest::GetAccountRateLimits { .. } => {
-                self.account_processor.get_account_rate_limits().await
+            ClientRequest::GetAccountRateLimits { params, .. } => {
+                self.account_processor.get_account_rate_limits(params).await
             }
             ClientRequest::ConsumeAccountRateLimitResetCredit { params, .. } => {
                 self.account_processor