## What changed
- Handle experimental `account/login/start` requests with `type: "amazonBedrock"`.
- Validate the API key and Mantle region, persist the managed credential, select the `amazon-bedrock` model provider, and emit the standard login and account-update notifications.
- Reload configuration for account and authentication status reads so the newly selected provider is visible immediately, with the startup configuration as a fallback.
- Extend the app-server test client with an Amazon Bedrock login mode that redacts API keys from request logs.
## Testing
- Add app-server coverage for successful login, credential and provider persistence, notifications, refreshed account state, invalid inputs, conflicting configuration, forced ChatGPT login, external authentication, and configuration reload failure.
GitOrigin-RevId: bf3ae98375caee41e78d2cdc677127138184c17a