On AMD GPUs with GNOME/Wayland, the hardware cursor plane can be
dropped on login or wake, leaving the cursor invisible until the
compositor recovers. Setting MUTTER_DEBUG_ENABLE_ATOMIC_KMS=0 in
/etc/environment disables atomic KMS in Mutter and prevents this.

The fix is only applied when an AMD GPU is detected via lspci and
is idempotent (skipped if already present in /etc/environment).

Validated with bash scripts/check.sh.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>