[app-server] Include reset-credit details in rate limits (#30395)

## Why

Supported clients currently receive only a reset-credit count from
`account/rateLimits/read`. The redemption UI and other app-server
clients need each available credit's expiry and ID so they can explain
what will expire and consume the credit a user selected. This
information belongs on the existing rate-limit read surface rather than
a second app-server list RPC that clients would need to coordinate.

## What changed

- extend `rateLimitResetCredits` on `account/rateLimits/read` with
nullable `credits` detail rows
- fetch usage and reset-credit details concurrently; if the detail
request fails, times out, or cannot be parsed, preserve the usage
response and return `credits: null`
- expose each credit's ID, reset type, status, grant time, expiry time,
title, and description
- add an optional nullable `creditId` to
`account/rateLimitResetCredit/consume`; omitting it preserves the
existing automatic-selection behavior
- forward a selected credit ID to the Codex backend and update the
app-server documentation and generated schemas

The TUI consumer is stacked in #30488.

## Validation

- `just test -p codex-app-server-protocol` (251 passed)
- `just test -p codex-backend-client` (16 passed)
- `just test -p codex-app-server rate_limit` (18 passed)

Part of #29618.

codex-rs/app-server/src/request_processors/account_processor.rs

@@ -891,9 +891,11 @@ impl AccountRequestProcessor {
         let client = BackendClient::from_auth(self.config.chatgpt_base_url.clone(), &auth)
             .map_err(|err| internal_error(format!("failed to construct backend client: {err}")))?;
 
-        let response = client
-            .get_rate_limits_with_reset_credits()
-            .await
+        let (response, detailed_rate_limit_reset_credits) = tokio::join!(
+            client.get_rate_limits_with_reset_credits(),
+            Self::detailed_rate_limit_reset_credits(&client),
+        );
+        let response = response
             .map_err(|err| internal_error(format!("failed to fetch codex rate limits: {err}")))?;
         if response.rate_limits.is_empty() {
             return Err(internal_error(
@@ -920,6 +922,15 @@ impl AccountRequestProcessor {
             .cloned()
             .unwrap_or_else(|| response.rate_limits[0].clone());
 
+        let rate_limit_reset_credits = detailed_rate_limit_reset_credits.or_else(|| {
+            response
+                .rate_limit_reset_credits
+                .map(|summary| RateLimitResetCreditsSummary {
+                    available_count: summary.available_count,
+                    credits: None,
+                })
+        });
+
         Ok(GetAccountRateLimitsResponse {
             rate_limits: rate_limits.into(),
             rate_limits_by_limit_id: Some(
@@ -928,11 +939,7 @@ impl AccountRequestProcessor {
                     .map(|(limit_id, snapshot)| (limit_id, snapshot.into()))
                     .collect(),
             ),
-            rate_limit_reset_credits: response.rate_limit_reset_credits.map(|summary| {
-                RateLimitResetCreditsSummary {
-                    available_count: summary.available_count,
-                }
-            }),
+            rate_limit_reset_credits,
         })
     }