Invoke loginctl, systemctl and moonlock via PATH

The absolute /usr/bin paths assume an FHS layout, so every power action
failed on NixOS with os error 2.

Cargo.lock

@@ -616,7 +616,7 @@ dependencies = [
 
 [[package]]
 name = "moonset"
-version = "0.9.1"
+version = "0.9.2"
 dependencies = [
  "dirs",
  "gdk-pixbuf",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "moonset"
-version = "0.9.1"
+version = "0.9.2"
 edition = "2024"
 description = "Wayland session power menu with GTK4 and Layer Shell"
 license = "MIT"

src/power.rs

@@ -112,7 +112,7 @@ fn run_command(action: &'static str, program: &str, args: &[&str]) -> Result<(),
 /// moonlock runs independently until the user unlocks.
 pub fn lock() -> Result<(), PowerError> {
     log::debug!("Power action: lock (spawning moonlock)");
-    Command::new("/usr/bin/moonlock")
+    Command::new("moonlock")
         .stdin(Stdio::null())
         .stdout(Stdio::null())
         .stderr(Stdio::inherit())
@@ -148,7 +148,7 @@ fn resolve_logout_command(
 
     match session_id {
         Some(id) if !id.is_empty() => Ok(vec![
-            "/usr/bin/loginctl".to_string(),
+            "loginctl".to_string(),
             "terminate-session".to_string(),
             id.to_string(),
         ]),
@@ -173,17 +173,17 @@ pub fn logout() -> Result<(), PowerError> {
 
 /// Hibernate the system via systemctl.
 pub fn hibernate() -> Result<(), PowerError> {
-    run_command("hibernate", "/usr/bin/systemctl", &["hibernate"])
+    run_command("hibernate", "systemctl", &["hibernate"])
 }
 
 /// Reboot the system via systemctl.
 pub fn reboot() -> Result<(), PowerError> {
-    run_command("reboot", "/usr/bin/systemctl", &["reboot"])
+    run_command("reboot", "systemctl", &["reboot"])
 }
 
 /// Shut down the system via systemctl.
 pub fn shutdown() -> Result<(), PowerError> {
-    run_command("shutdown", "/usr/bin/systemctl", &["poweroff"])
+    run_command("shutdown", "systemctl", &["poweroff"])
 }
 
 #[cfg(test)]
@@ -237,7 +237,7 @@ mod tests {
     #[test]
     fn logout_default_uses_loginctl_with_session_id() {
         let parts = resolve_logout_command(None, Some("3")).unwrap();
-        assert_eq!(parts, vec!["/usr/bin/loginctl", "terminate-session", "3"]);
+        assert_eq!(parts, vec!["loginctl", "terminate-session", "3"]);
     }
 
     #[test]