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/src/config/mod.rs

@@ -268,7 +268,6 @@ pub struct Config {
     /// Additional filenames to try when looking for project-level docs.
     pub project_doc_fallback_filenames: Vec<String>,
 
-    // todo(aibrahim): this should be used in the override model info
     /// Token budget applied when storing tool/function outputs in the context manager.
     pub tool_output_token_limit: Option<usize>,