fix: keep dry-run output valid json (#9823)

## Summary

- suppress human-readable reify diff lines when JSON output is requested
- preserve detailed diff output for non-JSON `--dry-run` and `--long`
commands
- cover both `--dry-run --json` and `--long --json`

## Background

Detailed dry-run diff output was introduced in npm 10.4.0 by #7133
without accounting for JSON mode. The structured JSON summary already
contains the add, remove, and change details, so the extra text is
redundant and makes stdout invalid JSON.

Related to #8567, with the regression coverage requested during review.

## Testing

- `tap --no-coverage --no-check-coverage test/lib/utils/reify-output.js`
- `eslint lib/utils/reify-output.js test/lib/utils/reify-output.js`

Fixes #8565

Copilot-Session: 48e629f8-eb5a-467c-970b-feb313628c00