Codex Desktop injects codex_app.automation_update with a large oneOf+$ref
schema. On xAI free/build Responses, that request accepts HTTP but never
emits SSE, so clients hang until cancel.
- Simplify automation_update (and similar large oneOf+$ref schemas) to a
permissive object schema before upstream xAI
- Map subscription free-usage-exhausted 429s to a 24h RetryAfter for
account rotation/cooldown
- Add unit tests for both behaviors