Inline 'settings' slash commands should be invokable at any point in prompt, and return to prompt

Feature Description

Typing /model in the middle of a prompt leaves it as a raw string, i should be able to invoke /model, go to model, change it, then return to my prompt as if nothing happened and i never typed /model.

Use Case

Often i find myself mid way through a prompt unable to switch my model, or do some settings lookup without removing my entire prompt, doing the lookup then repasting. Would be nice if it allowed that invocation mid way through a prompt, even if its just restricted to the hardcoded settings commands.

Additional Context

I want this ^^^

here:

How important is this to you?

Important for my workflow

未指定任何文件或测试。首先定位 prompt 输入处理以及现有的硬编码设置命令分发逻辑，然后跟踪命令执行如何改变 prompt 状态。完成的标准是：可以在 prompt 的中间调用 /model 和其他受支持的设置命令，同时原始 prompt 保持不变，并在之后恢复。