ExcelsiorCreative/EXCELSIOR-OS ? reverse-engineered prompt

Build me a web based desktop OS that feels like a mix of classic Mac and Windows, with a real desktop, draggable and resizable windows, a start or apple style menu, wallpapers, sounds, and a few theme choices like old Mac, Aqua, Windows XP, and Windows 98.

I want it to include a bunch of built in apps too, like a file manager, text editor, drawing app, music and video players, chat with an AI assistant, terminal, calendar, contacts, calculator, notes, and a simple game or two. Files should save in the browser by default, with backup and restore, and the AI should be able to help inside the system and some apps.

Make it work nicely on desktop and mobile, and if it makes sense, set it up so I can run it locally and self host it too. Use the docs online if you need to.