multi file apply_diff: missing side-by-side diff preview capability

[KJ7LNW]

Version: 3.22.3 (719d661)

Problem

The multi-file apply_diff experiment lacks a side-by-side diff preview capability. This prevents users from previewing changes before accepting them.

Technical Details

The current implementation in multiApplyDiffTool.ts supports modifying multiple files in a single operation:

<apply_diff>
<args>
<file>
  <path>file1.txt</path>
  <diff>...</diff>
</file>
<file>
  <path>file2.txt</path>
  <diff>...</diff>
</file>
<file>
  <path>file3.txt</path>
  <diff>...</diff>
</file>
</args>
</apply_diff>

However, the preview mechanism only shows the traditional search/replace format:

<<<<<<< SEARCH
Original content
=======
New content
>>>>>>> REPLACE

Suggested Implementation

A side-by-side diff preview for multi-file operations should:

1. Render a tabbed interface showing each file being modified
2. Display original and modified content in parallel columns for each file
3. Highlight specific changes with color coding
4. Provide file navigation controls for multi-file operations
5. Include a summary view showing all affected files

This would enhance the multi-file apply_diff experiment by providing proper visual feedback before changes are accepted.

[KJ7LNW]

@samhvw8 / others: I am working on this it will land in #3055 .