Add Support for AI Agent-Driven Change Proposals in AI Chat

[planger]

Enable AI agents to propose a set of changes directly within the AI chat interface. The proposed changes should support:

1. Generic Editable Elements:

   • Changes can target files or custom concepts.
   • A generic interface should allow for specific editable elements to be implemented, with customizable labels, icons, and actions.

2. User Interaction with Changes:

   • Display all elements with suggested changes, allowing users to open, review diffs, and decide whether to apply or reject changes.
   • Support for change types such as add, delete, and modify for each element.

Proposing changes from an AI agent solely through chat responses can quickly become unwieldy, especially when multiple changes span across several elements. Managing such proposals inline with chat responses can lead to confusion, as it becomes challenging to track the relationship between changes, navigate across modified elements, or grasp the overall context of the suggestions. Furthermore, refining the proposed changes often requires iterative feedback and adjustment, making it essential to have a dedicated, persistent, and structured view of the current state of suggestions. By decoupling these "current suggested changes" from specific chat responses and presenting them in a centralized location, users gain a clearer and more organized overview of all proposed changes, enabling better navigation, review, and decision-making.