## What changed
- Add the experimental `amazonBedrockAccessKeys` app-server login flow, persist its credentials in the configured auth store, and use them for SigV4-signed Bedrock requests.
- Report `bedrockAccessKeys` as a distinct auth mode and document access-key login alongside AWS profile and environment credential setup.
- Clear the selected Bedrock provider, AWS settings, and Bedrock-specific model on logout while leaving external AWS credentials and `.env` untouched.
- Reject managed access-key login when higher-precedence configuration would prevent its region or profile settings from taking effect.
## Testing
- Cover access-key login, storage, request signing, configuration conflicts, status reporting, and logout cleanup.
GitOrigin-RevId: bbf297887c6503d3651ceb2aad85c4d626e32723
## Why
Authentication mode is a domain concept used by login, model selection,
telemetry, and transports. Keeping the canonical type in app-server
protocol forces those lower-level crates to depend on an unrelated wire
API.
## What changed
- Added canonical `codex_protocol::auth::AuthMode` domain values.
- Kept the app-server wire DTO unchanged and added an explicit app-side
conversion.
- Removed production app-server-protocol dependencies from login,
model-provider-info, models-manager, and otel call paths.
## Stack
This is PR 2 of 6, stacked on [PR
#29714](https://github.com/openai/codex/pull/29714). Review only the
delta from `codex/split-json-rpc-protocols`. Next: [PR
#29722](https://github.com/openai/codex/pull/29722).
## Validation
- Auth and login coverage passed in the focused protocol/domain test
run.
- App-server account and auth conversion coverage passed.