[FEATURE] NotebookEdit: show inline diff when editing notebook cells

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When Claude edits a Jupyter notebook cell using NotebookEdit, it replaces the entire cell content without showing what changed. The user has no way to review a diff before the edit is applied and approve it.

Proposed Solution

When Claude edits a notebook cell, the user should be able to see exactly what changed (before/after) inline, similar to how edits to .py, .sql, and other text files are presented.

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

File operations

Use Case Example

Example scenario:

1. I'm working on a data analysis notebook with multiple cells containing chart code
2. Claude needs to fix a bug in a boxplot cell — changing 3 lines in a 30-line cell
3. With this feature, I could see exactly which lines changed (e.g. a method call replaced, a line added, a new cell created) before approving the changes.
4. This would save me time, reduce errors, and give me confidence in what's being changed. Currently I either have to manually compare the entire replaced cell to spot what changed, or ask Claude to describe the diff in text before applying — which is error-prone and breaks the review flow. With inline diffs I could understand the changes at a glance and catch unintended modifications before they're applied.

Additional Context

When editing regular files (.py, .sql, etc.), Claude's Edit tool shows a clear inline diff with old_string → new_string, making it easy to review. Notebooks are the only file type where edits are applied as full cell replacements with no diff visibility.