I want to build a native macOS app named JSONFormatter using Xcode, Swift, and SwiftUI. Use the attached sketch as the visual reference for the application.
Do not write, modify, or generate any code yet.
First, inspect the existing Xcode project and then produce a staged implementation plan. The plan should be detailed enough that each stage can be completed, built, and manually verified before moving to the next stage.
App requirements:
- Native macOS SwiftUI application
- Two-pane layout