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/app-server/tests/suite/v2/model_list.rs

@@ -64,7 +64,7 @@ async fn list_models_returns_all_models_with_large_limit() -> Result<()> {
                 },
                 ReasoningEffortOption {
                     reasoning_effort: ReasoningEffort::High,
-                    description: "Maximizes reasoning depth for complex problems".to_string(),
+                    description: "Greater reasoning depth for complex problems".to_string(),
                 },
                 ReasoningEffortOption {
                     reasoning_effort: ReasoningEffort::XHigh,
@@ -138,7 +138,7 @@ async fn list_models_returns_all_models_with_large_limit() -> Result<()> {
                 },
                 ReasoningEffortOption {
                     reasoning_effort: ReasoningEffort::High,
-                    description: "Maximizes reasoning depth for complex or ambiguous problems"
+                    description: "Greater reasoning depth for complex or ambiguous problems"
                         .to_string(),
                 },
                 ReasoningEffortOption {