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/core/tests/suite/list_models.rs

@@ -79,7 +79,7 @@ fn gpt_5_1_codex_max() -> ModelPreset {
             ),
             effort(
                 ReasoningEffort::High,
-                "Maximizes reasoning depth for complex problems",
+                "Greater reasoning depth for complex problems",
             ),
             effort(
                 ReasoningEffort::XHigh,
@@ -162,7 +162,7 @@ fn gpt_5_2() -> ModelPreset {
             ),
             effort(
                 ReasoningEffort::High,
-                "Maximizes reasoning depth for complex or ambiguous problems",
+                "Greater reasoning depth for complex or ambiguous problems",
             ),
             effort(
                 ReasoningEffort::XHigh,