## What changed
- Advertise `supportsDeviceAuth` in `account/gatewayOAuth/read` and accept `deviceAuth: true` in `account/gatewayOAuth/login`.
- Return a device prompt with `verificationUrl`, `userCode`, and `loginId` before approval, then notify the initiating connection of success or failure with the matching `loginId`.
- Reuse or refresh saved credentials when possible, returning `prompt: null` without another device authorization. Update protocol schemas, generated bindings, and documentation.
## Testing
Add an integration test covering the device prompt, correlated completion notification, capability reporting, and token refresh without another device grant.
GitOrigin-RevId: 6ecc38c9baadcfda3272654ed71e4aaa431421bf