feat: add shortcut-manager for GNOME keybinding presets

presets.py

@@ -0,0 +1,23 @@
+"""
+Quick-fill command presets for the shortcut manager's "new shortcut" dialog.
+Only offered when the underlying binary is actually installed, so the list
+never suggests a dead command. Purely a convenience for the command entry -
+any preset is still just a plain command string once saved.
+"""
+
+import shutil
+
+_CANDIDATES = [
+    ("Terminal", "gnome-terminal", "gnome-terminal"),
+    ("File manager", "nemo", "nemo"),
+    ("Lock screen", "cinnamon-screensaver-command", "cinnamon-screensaver-command --lock"),
+    ("Screenshot - area", "flameshot", "flameshot gui"),
+    ("Screenshot - full screen", "gnome-screenshot", "gnome-screenshot"),
+    ("Web browser", "xdg-open", "xdg-open http://"),
+    ("Mute volume toggle", "amixer", "amixer -q set Master toggle"),
+    ("Text editor", "gedit", "gedit"),
+]
+
+
+def availablePresets():
+    return [(label, command) for label, binary, command in _CANDIDATES if shutil.which(binary)]