PLEASE explose long context toggle in the composer directly, just like reason...

PLEASE explose long context toggle in the composer directly, just like reasoning level. It is so annoying to have to navigate through the nested pop-ups to toggle it on the fly-out pop-up on the model and then click back in to select that model

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| Field | Value |
| --- | --- |
| App version | 1.1.2 |
| OS | Windows 10.0.26200 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Week 8 |

从 /chat 路径开始，检查 composer 和模型选择控件，并以现有的 reasoning-level 控件作为位置参考。完成的标准是：无需在嵌套弹出窗口之间导航，即可直接在 composer 中使用 long-context 开关，并且可以在撰写过程中更改。

由索引模型根据 Issue 内容生成。