- Updated the diff generation in `edit.ts` and `write-file.ts` to include the `ignoreWhitespace: true` option.
- This ensures that whitespace-only changes are not highlighted in the diff output when there are other content modifications, making the diffs cleaner and easier to review.
- Extract default diffing options into single source of truth.
Fixes https://github.com/google-gemini/gemini-cli/issues/548
