Quickly switch between pre-set model configs

### Describe the feature or problem you'd like to solve

Enable rapid model/effort switching for better efficiency

### Proposed solution

As developer I want in many cases to use the strongest model with highest effort level available. However, typing /model, choosing the model with arrows, then choosing the effort level with right left is cumbersome and might cause be to avoid it and therefore not use the right model for the task.

My proposal is to enable mapping keyboard shortcuts to pre-set models and effort so I can quickly switch between them based on the task.
I assume there are other use cases for custom keyboard mapping.

Alternatively, add option to create custom commands, like for example "/cheap" will switch to a pre-set model I choose with pre-set effort level.
Using an approach like "/agent cheap" can work but it changes tools/behavior and not generic enough.

Another option is to create another command (e.g. "/pmodel") which shows a list of 5 pre-set model configurations I can quickly choose by number.

### Example prompts or workflows

_No response_

### Additional context

_No response_

issue 中沒有指定檔案、測試或進入點。先定位現有的 /model 流程，以及任何鍵盤快速鍵或自訂命令的處理邏輯。將提議的方法與目前的 CLI 行為進行比較；done 應提供一種在預設的模型與 effort 設定之間快速切換的方式。

由索引模型根據 Issue 內容生成。