Override truncation policy at model info level (#8856)

We used to override truncation policy by comparing model info vs config
value in context manager. A better way to do it is to construct model
info using the config value

codex-rs/core/tests/suite/mod.rs

@@ -35,6 +35,7 @@ mod json_result;
 mod list_dir;
 mod list_models;
 mod live_cli;
+mod model_info_overrides;
 mod model_overrides;
 mod model_tools;
 mod models_etag_responses;