signalapp/Signal-Desktop ? reverse-engineered prompt

Build me a desktop version of the Signal private messenger. It needs to work on Windows, macOS, and Linux. The most important feature is that it has to link with the Signal app on my phone (either Android or iOS) so I can send and receive all my encrypted messages from my computer.

I want a clean, native-feeling application that lets me manage my private conversations just like I would on mobile. It should feel like a true desktop counterpart to the phone app, not just a web wrapper. You can look up any specifics about how the Signal protocol or device linking works if you need to. The main goal is a secure, cross-platform messaging client that syncs with an existing mobile account.