Add a "Discuss" Mode

Feature Description

Add a "Discuss" mode where bot doesn't write any plan after some idea immediately or start implementing it . In Discuss mode it will make suggestion, ask question, improve the understanding of feature that user want to implement.

Use Case

I will be super effective where user continuedly toggle discuss to code or code to discuss or user can discuss for long time then proceed to make a plan. Its super important to discuss the implementation after implementing a big plan where there is 10+ to-dos to understand what actually happened. Right now it can be done but in plan mode it sometimes write a plan or in coding mode it write code. Discuss mode will be fully free from editing anything

Additional Context

I needed to make a skill for Discuss mode but its not efficient and also sometimes forgot to activate the skill or need to say lets discuss but when u go back and forth with coding then discussing and then coding discussing again it become irritating.

How important is this to you?

Important for my workflow

首先定位現有的 plan 和 coding 模式處理邏輯以及模式切換流程。追蹤 prompt 的路由方式，以及如何阻止在非 coding 模式下進行編輯。完成的標準是：使用者可以進入 Discuss 模式，在不產生計畫或編輯檔案的情況下接收建議和問題，並可靠地切換回 plan 或 coding 模式。