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.

从 /terminal-setup 入口点开始，复现 macOS 上 iTerm2 中 Shift-Enter 的行为。调查那里的终端输入是如何处理的；当 Shift-Enter 插入换行而不提交命令时，即表示完成。

由索引模型根据 Issue 内容生成。