feat(tui) /personality (#9718)

## Summary
Adds /personality selector in the TUI, which leverages the new core
interface in #9644

Notes:
- We are doing some of our own state management for model_info loading
here, but not sure if that's ideal. open to opinions on simpler
approach, but would like to avoid blocking on a larger refactor
- Right now, the `/personality` selector just hides when the model
doesn't support it. we can update this behavior down the line

## Testing
- [x] Tested locally
- [x] Added snapshot tests

codex-rs/app-server/src/models.rs

@@ -28,6 +28,7 @@ fn model_from_preset(preset: ModelPreset) -> Model {
             preset.supported_reasoning_efforts,
         ),
         default_reasoning_effort: preset.default_reasoning_effort,
+        supports_personality: preset.supports_personality,
         is_default: preset.is_default,
     }
 }