### Why
Auto-review is the user-facing name for the approvals reviewer, but the
config/API value still exposed the old `guardian_subagent` name. That
made new configs and generated schemas point users at Guardian
terminology even though the intended product surface is Auto-review.
This PR updates the external `approvals_reviewer` value while preserving
compatibility for existing configs and clients.
### What changed
- Makes `auto_review` the canonical serialized value for
`approvals_reviewer`.
- Keeps `guardian_subagent` accepted as a legacy alias.
- Keeps `user` accepted and serialized as `user`.
- Updates generated config and app-server schemas so
`approvals_reviewer` includes:
- `user`
- `auto_review`
- `guardian_subagent`
- Updates app-server README docs for the reviewer value.
- Updates analytics and config requirements tests for the canonical
auto_review value.
### Compatibility
Existing configs and API payloads using:
```toml
approvals_reviewer = "guardian_subagent"
```
continue to load and map to the Auto-review reviewer behavior.
New serialization emits:
```toml
approvals_reviewer = "auto_review"
```
This PR intentionally does not rename the [features].guardian_approval
key or broad internal Guardian symbols. Those are split out for a
follow-up PR to keep this migration small and avoid touching large
TUI/internal surfaces.
**Verification**
cargo test -p codex-protocol
approvals_reviewer_serializes_auto_review_and_accepts_legacy_guardian_subagent
cargo test -p codex-app-server-protocol
approvals_reviewer_serializes_auto_review_and_accepts_legacy_guardian_subagent
46142c3cb0