## What changed
- Carry optional backend-owned banner and account identity data through
`account/rateLimits/read`, filtering banners that do not match the authenticated
account and user.
- Render supported rate-limit notices above the composer with actions for usage,
credits, resets, owner notifications, and plan management while preserving the
existing fallback UI for absent or unsupported banners.
- Refresh usage after limit errors, reject stale responses, and keep queued input
paused until recovery completes. When instructed by the banner, switch to the
first available fallback model without changing unrelated thread settings.
## Testing
- Add protocol, banner parsing and rendering, CTA, identity filtering, refresh
ordering, fallback-model, account-change, and queued-input recovery coverage.
GitOrigin-RevId: e03d75a82e425deb87f4b120a71cf2286c0ef6cc
79b04f1ab5