Qt, not QT. It's pronounced as "cute", not Q, T.

And no, Satoshi was not a vibe-coder.

Forms for GUI application usually are done visually, and then the low level code is generated from a tool of the GUI framework.

As an example, you can see all these forms (.ui files) from the current Bitcoin Core implementation using Qt here: https://github.com/bitcoin/bitcoin/tree/master/src/qt/forms

These .ui files are created with a GUI (Qt Creator), and then the MOC (Meta-Object Compiler) generates the required code from them.

All of this is not "vibe coding", it's standard GUI programming.