Classify streaming rate-limit errors (#40931)

## What changed

- Classify `response.failed` events with the `rate_limit_exceeded` code as a distinct retryable error while preserving any parsed retry delay.
- Expose the error as `rateLimitExceeded` through the core protocol and app-server schemas after stream retries are exhausted.
- Preserve the upstream message for TUI display while keeping it out of telemetry summaries.

## Testing

- Cover SSE classification, retry metadata, protocol conversion and serialization, exhausted stream retries, telemetry redaction, and TUI rendering.

GitOrigin-RevId: 02dab4d3477dcd7653a58c49c4bd38687a616579

codex-rs/codex-api/src/error.rs

@@ -23,6 +23,11 @@ pub enum ApiError {
         message: String,
         delay: Option<Duration>,
     },
+    #[error("rate limit exceeded: {message}")]
+    RateLimitExceeded {
+        message: String,
+        delay: Option<Duration>,
+    },
     #[error("rate limit: {0}")]
     RateLimit(String),
     #[error("invalid request: {message}")]