scratchfoundation/scratch-editor ? reverse-engineered prompt

Build me a Scratch editor that feels like the one on the Scratch website, with the main interface for creating and editing projects, a stage that shows sprites and backdrops, a costume and backdrop drawing area, and support for loading project assets like images and sounds. I want the core editor pieces separated in a sensible way so the UI, rendering, storage, paint tools, and project execution can work together cleanly. It should be able to run Scratch projects, draw SVG and bitmap artwork, and handle the basic menus, buttons, and editing tools people expect when making a project.

If you need to, look up current docs online for any Scratch details that are missing, then implement the app in a way that is easy to develop and test in this monorepo. Please keep it practical and make it something I can run locally and extend later.