fix: stop double-reading trackpad under Wayland (evdev + wl_pointer)
Under cage, libinput grabs keyboard/mouse/touchpad and delivers them
via wl_pointer_motion (absolute coords). The evdev fallback was ALSO
reading the same devices and applying relative deltas on top, causing
progressive cursor drift that worsened over time.
Skip evdev polling entirely under Wayland — only read NuPhy hidraw.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>