2.0.3 — live-USB copy step fixed

AsahiLocker 2.0.3 — the live-USB copy step, fixed

Documentation only. Nothing changes in how a volume is encrypted, in the
KDF, or in any volume an earlier release made.

What was wrong

The copy onto the stick silently did nothing (#3). INSTALL.md and
LIVE-USB.md said to run sudo ./build.sh mount. The USB builder refuses to
run under sudo: it prints a one-line notice and exits successfully. So
nothing was mounted, and the cp that followed created an ordinary
mnt_usb/root/ folder on the build machine. The stick booted fine, then
luks-deploy.sh was command not found.

The fallback could not work. Step 3 offered mounting subvol=root and
running the script from /mnt/home/<user>/. Fedora Asahi keeps /home in
its own home subvolume, so that folder is empty. And the script must
unmount the target before encrypting it, which it cannot do while running
from it.

The steps now

• Copy step: run ./build.sh mount from the root shell you built in,
  with no sudo. findmnt mnt_usb must print a line before you copy, and
  an ls afterwards confirms the script landed.
• Already booted the stick without it? No rebuild needed. Mount the
  internal home subvolume, copy AsahiLocker to /root, unmount, run. See
  docs/INSTALL.md → Step 3.

Thanks to @jbArchNovice for reporting it and for sticking with it.