fix: don't wake displays on input device removal, count input wakes as activity

A sleeping wireless keyboard relit blanked displays and idle never re-armed.

Written with assistance from Claude Opus 5.0. Reviewed, built and tested by the
author, who understands the changes in full.

src/input/mod.rs

@@ -220,7 +220,16 @@ impl State {
     ) where
         <B as InputBackend>::Device: 'static,
     {
-        crate::wayland::handlers::output_power::set_all_surfaces_dpms_on(self);
+        // An input device going away is not user activity, e.g. a wireless keyboard
+        // dropping its link when it sleeps, so it must not power displays back on.
+        // Device additions still wake: after a system resume the re-enumerated
+        // devices may be the only input seen, and the wake resets idle anyway.
+        if !matches!(
+            &event,
+            InputEvent::DeviceRemoved { .. } | InputEvent::Special(_)
+        ) {
+            crate::wayland::handlers::output_power::set_all_surfaces_dpms_on(self);
+        }
 
         use smithay::backend::input::Event;
         match event {

src/wayland/handlers/output_power.rs

@@ -21,6 +21,11 @@ pub fn set_all_surfaces_dpms_on(state: &mut State) {
     }
 
     if changed {
+        // Powering an output on because of input is activity. Without this the idle
+        // notifier stays idled, the idle daemon never sees `resumed`, and nothing
+        // powers the output off again until real input arrives.
+        let seat = state.common.shell.read().seats.last_active().clone();
+        state.common.idle_notifier_state.notify_activity(&seat);
         OutputPowerState::refresh(state);
     }
 }