feat: add new config option: model_supports_reasoning_summaries (#1524)

As noted in the updated docs, this makes it so that you can set:

```toml
model_supports_reasoning_summaries = true
```

as a way of overriding the existing heuristic for when to set the
`reasoning` field on a sampling request:


https://github.com/openai/codex/blob/341c091c5b09dc706ab5c7d629516e6ef5aaf902/codex-rs/core/src/client_common.rs#L152-L166

codex-rs/core/src/codex.rs

@@ -586,7 +586,7 @@ async fn submission_loop(
                 }
 
                 let client = ModelClient::new(
-                    model.clone(),
+                    config.clone(),
                     provider.clone(),
                     model_reasoning_effort,
                     model_reasoning_summary,