[FEATURE] Clearly show what changes were made to a plan between iterations

### Preflight Checklist

- [ ] I have searched [existing requests](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20label%3Aenhancement) and this feature hasn't been requested yet
- [x] This is a single feature request (not multiple features)

### Problem Statement

When in plan mode, Claude often comes up with a quite comprehensive plan and asks for comments. After submitting comments, Claude presents its updated plan, which oftern 80-90% identical to the previous one, but with some changes to accommodate the request.

It would be nice if it was clearly indicated what was removed, changed, added (similar to a code diff) to the plan since the previous version.

### Proposed Solution

Either an inline indication or a side by side diff like view

### Alternative Solutions

_No response_

### Priority

Medium - Would be very helpful

### Feature Category

Interactive mode (TUI)

### Use Case Example

Im planning a new feature, but dont want to read through the entire plan top-bottom when just minor changes has been made

### Additional Context

_No response_

Start by locating the plan-mode TUI entry point and how the previous and updated plans are rendered. The feature is done when users can clearly identify removed, changed, and added plan content without rereading the entire plan.

Written by the indexing model from the issue text.