Replace npm-run-all dependency with npm-run-all2

[chrispcampbell]

The npm-run-all2 package is a maintained fork of npm-run-all. It's a drop-in replacement, has fewer dependencies, and does not rely on the older versions of cross-spawn which have reported vulnerabilities. We should be able to switch without any compatibility issues. We only use it for the run-s command in various package.json scripts.

[chrispcampbell]

The new package has many fewer dependencies than the old, so the lock file shrinks by ~500 lines.

[chrispcampbell]

Claude-generated summary:

The npm-run-all2 package is a maintained fork of npm-run-all. It is a drop-in replacement, has fewer dependencies, and does not rely on the older versions of cross-spawn that have reported vulnerabilities.

Note that we use the 8.x version (instead of the latest 9.x) because 9.x requires Node 22.22.2 or later, which is stricter than the Node version required by this project.