Add Linux support via evdev

[Copilot]

Mouser only worked on Windows and macOS. This adds Linux support across all platform-specific modules.

Changes

core/config.py

• Linux config stored at ~/.config/Mouser, respecting $XDG_CONFIG_HOME

core/app_detector.py

• Detects active window via xdotool getactivewindow getwindowpid → /proc/<pid>/comm
• Falls back to wmctrl -lp + xprop -root _NET_ACTIVE_WINDOW
• PID values are validated as digits-only before use in /proc paths

core/key_simulator.py

• Lazy-initialized evdev.UInput virtual keyboard for kernel-level key injection (works on X11 and Wayland)
• 22 actions mapped to Linux conventions: Ctrl instead of Cmd, KEY_LEFTMETA for Super/Win, native media/browser keys

core/mouse_hook.py

• Discovers all pointer devices in /dev/input (requires BTN_LEFT + REL_X/Y)
• Grabs each device exclusively; creates a matching UInput passthrough so the pointer keeps working
• Handles BTN_MIDDLE, BTN_SIDE/BTN_BACK, BTN_EXTRA/BTN_FORWARD, hi-res REL_HWHEEL
• Gesture direction tracking (same algorithm as macOS) via accumulated REL_X/Y per sync frame
• Scroll inversion applied at UInput write time
• Integrates with HidGestureListener for the MX Master 3S gesture button (HID++ protocol)

requirements.txt

evdev>=1.6.0; sys_platform == "linux"

Required Linux setup

sudo usermod -aG input $USER    # read /dev/input
sudo usermod -aG uinput $USER   # write /dev/uinput
sudo apt install xdotool         # or: wmctrl x11-utils (app auto-switching)

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