How to reproduce:
1. Install 6000.7.0a6
2. Open Unity.app/Contents/Resources/PackageManager/BuiltInPackages/com.unity.inputsystem
3. Observe the results
Expected results: Only shippable package content is present, as it is for the other
built-in packages
Actual results: ".npmignore", ".gitignore" and ".migrationtracker" are present in the
installed Editor, and ".migrationtracker" is listed in the package's own ".npmignore"
exclude list
Reproducible with: 6.7.0 (6000.7.0a6)
Not reproducible with: 1.19.0 (6000.7.0a5)
Reproducible on: macOS Tahoe 26.6.2 (M1 Max)
Not reproducible on: No other environment tested