Global shortcut setup (.desktop file + platform docs)

[pgivel]

Summary

Provide a way to launch Screen Ruler with a global keyboard shortcut, without requiring a persistent daemon.

Approach

Linux

• Ship a .desktop file (screen-ruler.desktop) with the appropriate Exec= line.
• Document how to bind it to a shortcut in common DEs:
  • GNOME: gsettings set org.gnome.settings-daemon.plugins.media-keys.custom-keybinding:/org/gnome/settings-daemon/plugins/media-keys/custom-keybindings/custom0/ ...
  • KDE: System Settings → Shortcuts → Custom Shortcuts
  • Hyprland/Sway: bind directive in config

macOS

• Document using Automator / Shortcuts app to wrap the CLI command.
• Optionally explore CGEventTapCreate for native registration.

Windows

• Document binding via Settings → Keyboard → Keyboard Shortcuts.
• Optionally provide a .lnk shortcut file.

Non-goals (for now)

• No persistent daemon or tray icon — the app lifecycle stays ephemeral (capture → measure → quit).
• A daemon approach (e.g. pystray + pynput) could be explored later for faster launch if the ~200ms capture time becomes a concern.