## What changed
- Add the disabled-by-default `features.credential_masking` flag to enable credential brokerage through an already enabled network proxy, retaining custom credential providers and managed configuration precedence.
- Prevent project configuration from overriding credential masking and apply existing credential-broker protections to project shell settings when masking is enabled.
- Keep brokerage inactive when the proxy is disabled. Warn at startup and after permission-profile changes when masking is inactive because sandboxing or the proxy is disabled, or provider environment keys conflict.
## Testing
Add coverage for configuration precedence, project protections in both configuration loaders, permission-profile transitions, inactive-masking warnings, and shell snapshot masking of built-in and custom credentials.
GitOrigin-RevId: 4bcb293356e8c1524bdaa4f1b95cbc1e935a5271
Winston Howes
bd274564e1