[Feature]: Show changed files from repositories modified by the agent

Description

I use T3 Code with multiple separate Git repositories.

One repository acts as a central context and knowledge repository. It contains project instructions, documentation, shared context, and information used by the agent.

Other repositories contain the actual applications being developed.

For example:

context-repository/
application-repository/

The active T3 Code project is the context repository because it contains the instructions and project information needed by the agent. However, I often ask the agent to modify files in a separate application repository.

The agent can successfully edit files in the application repository, but the Changed files panel continues to show only changes from the active context repository.

Current behavior

1. The active T3 Code project is the context repository.
2. The agent modifies files in a separate application repository.
3. The agent confirms that files in the application repository were changed.
4. The Changed files panel shows only changes from the active context repository.
5. The changes in the application repository are missing from the panel.

Expected behavior

The Changed files panel should detect and display changes based on the repositories and files actually modified by the agent during the thread.

Ideally, T3 Code should:

1. Show changed files grouped by repository.
2. Automatically detect which Git repository was modified.
3. Provide a repository selector in the Changed files panel.
4. Show a clear notice when the agent modifies files outside the active workspace, with an option to open that repository's diff.

For example:

context-repository
  No changes

application-repository
  src/components/Example.astro
  src/pages/index.astro

Why this matters

The current behavior makes it difficult to verify the agent's work. It can create the impression that no changes were made, or that the wrong files were modified.

This is especially problematic for workflows where one central repository contains the agent's instructions and project context, while implementation happens in separate application repositories.

The active workspace should be allowed to remain responsible for context and instructions, while the change review interface should still display modifications made in other repositories.

Possible implementation direction

T3 Code could track the Git repositories touched during the thread and expose their changes in the Changed files panel.

Alternatively, T3 Code could display a repository selector next to the current Changed files panel.

Environment

• T3 Code
• Windows
• Multiple local Git repositories
• One repository used for agent context and instructions
• One or more separate repositories used for application development

Start by tracing the Changed files panel and the Git repository or diff handling used by the active T3 Code project. Reproduce the workflow with a context repository and a separate application repository, then define how repositories touched during a thread are detected and displayed. Done means changes are reviewable and clearly associated with the repository where they occurred.