## 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.
## Why
Codex users can earn personal rate-limit reset credits, but app-server
clients do not currently have an API for reading or redeeming them. This
adds the backend and protocol foundation used by the `/usage` TUI flow
in #28154.
## What changed
- Extend `account/rateLimits/read` with a nullable
`rateLimitResetCredits` summary sourced from the existing usage
response.
- Add backend-client and app-server support for consuming a reset with a
caller-generated idempotency key. A UUID is recommended, and clients
reuse the same key when retrying the same logical reset.
- Return only the consume `outcome`; clients refetch
`account/rateLimits/read` for updated window state.
- Document the response field and each consume outcome, and regenerate
the JSON and TypeScript schema fixtures.
- Clarify in `AGENTS.md` that new app-server string enum values use
camelCase on the wire.
- Update the existing TUI response fixture for the expanded protocol
shape.
- Add coverage for authentication, response mapping, backend failures,
consume outcomes, and request timeout behavior.
## Validation
- `just test -p codex-app-server-protocol` — 231 passed.
- `just test -p codex-backend-client` — 14 passed.
- Focused `codex-app-server` reset-credit tests — 5 passed.
- Focused `codex-tui` protocol response fixture test — passed.
- `just fix -p codex-backend-client -p codex-app-server-protocol -p
codex-app-server` — passed.
- `just fmt` — passed.
