Setup Timeshift on Debian forky with btrfs root

By default, the Debian installer names the root subvolume @rootfs. However, Timeshift has a hardcoded requirement looking exclusively for a subvolume named @ (and optionally @home). The core post installation hack was proposed by Google AI Assistant. I've added just one command to second part related with creating @home. The most important step is "The GRUB Edit Route"