Support iTerm2 terminal on Mac with /terminal-setup

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

I want to use - for newlines in my input without CLI interpreting it as input

### Proposed solution

_No response_

### Example prompts or workflows

_No response_

### Additional context

This used to work until a recent build - Shift-Enter gave me a new line in input without sending the command. So it feels like a regression.

從 /terminal-setup 入口點開始，重現 macOS 上 iTerm2 中 Shift-Enter 的行為。調查那裡的終端輸入是如何處理的；當 Shift-Enter 插入換行而不提交命令時，即表示完成。

由索引模型根據 Issue 內容生成。