Fix misleading 'maximize' high effort description on xhigh models (#7874)

## Notes
- switch misleading High reasoning effort descriptions from "Maximizes
reasoning depth" to "Higher reasoning depth" across models with xhigh
reasoning. Affects GPT-5.1 Codex Max and Robin
- refresh model list fixtures and chatwidget snapshots to match new copy

## Revision
- R2: Change 'Higher' to 'Greater'
- R1: Initial

## Testing

<img width="583" height="142" alt="image"
src="https://github.com/user-attachments/assets/1ddd8971-7841-4cb3-b9ba-91095a7435d2"
/>

<img width="838" height="142" alt="image"
src="https://github.com/user-attachments/assets/79aaedbf-7624-4695-b822-93dea7d6a800"
/>

codex-rs/tui/src/chatwidget/tests.rs

@@ -1930,7 +1930,7 @@ fn single_reasoning_option_skips_selection() {
 
     let single_effort = vec![ReasoningEffortPreset {
         effort: ReasoningEffortConfig::High,
-        description: "Maximizes reasoning depth for complex or ambiguous problems".to_string(),
+        description: "Greater reasoning depth for complex or ambiguous problems".to_string(),
     }];
     let preset = ModelPreset {
         id: "model-with-single-reasoning".to_string(),