Light the screen (dimmed) while a Notification's Toast shows

An Off screen turns on dimmed for the Toast's duration so the user can
see what beeped. It isn't user activity: the timeouts aren't restarted,
and a key pressed meanwhile reaches the App.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

lib/services/src/power_policy.h

@@ -19,6 +19,14 @@ class PowerPolicy {
     // Records a key press. Returns true if the key only woke an Off screen and must not reach the App.
     bool activity(uint32_t nowMs);
 
+    // A Notification is showing until untilMs: an Off screen lights up Dimmed meanwhile. It's not
+    // user activity, so it doesn't restart the timeouts.
+    void notify(uint32_t nowMs, uint32_t untilMs) {
+        (void)nowMs;
+        notifyUntilMs_ = untilMs;
+        notifying_ = true;
+    }
+
     ScreenState update(uint32_t nowMs);
     ScreenState state() const { return state_; }
 
@@ -26,6 +34,8 @@ class PowerPolicy {
     uint32_t dimMs_;
     uint32_t offMs_;
     uint32_t lastActivityMs_ = 0;
+    uint32_t notifyUntilMs_ = 0;
+    bool notifying_ = false;
     ScreenState state_ = ScreenState::On;
 };