Gaze: idle while the gaze isn't used

The gaze service ran ft-gaze and our own eye tracker all the time: with gaze mode off, ft-eyes
still took about 60% of a core, and ft-eyegrab, ft-gaze and ft-gazed 3 to 4% each. Now ft-gaze
and our tracker run only while gaze mode is on and someone wears the headset, while a check or
the calibration is open or asked for, or under a "wake" lease, which the Gaze page of Frametop
Input Settings renews while it's open. 30 s after the last use they stop, and the frame grabber
idles with our tracker.

- The pointer helper answers "gaze ? headset" with worn|away (SteamVR's activity level for the
  headset); an older helper answers it as before, and the service then goes by gaze mode alone.
- A quick check, calibration, or fit check asked for while idle wakes the tracker and opens once
  it sends; the automatic calibration waits quietly while it starts.
- Status has "awake" and "idle" (why), and the Gaze page shows it.
- gaze/test/idle-test.py runs the service with a fake helper and ft-gaze, offline.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

input-settings/main.qml

@@ -969,6 +969,14 @@ Kirigami.ApplicationWindow {
             title: "Gaze"
             header: DriverWarning {}
             property var status: backend.gazeStatus
+            // The gaze service idles while the gaze isn't used; open, this page keeps it going.
+            Timer {
+                running: true
+                repeat: true
+                interval: 10000
+                triggeredOnStart: true
+                onTriggered: backend.keepGazeAwake()
+            }
             actions: [
                 Kirigami.Action {
                     text: "Quick check"
@@ -1202,7 +1210,8 @@ Kirigami.ApplicationWindow {
                 Controls.Label {
                     Kirigami.FormData.label: "Service:"
                     text: backend.gazeServiceRunning
-                          ? (gpage.status.ft_gaze ? "running" : "running, eye tracker reader restarting")
+                          ? (gpage.status.awake === false ? "idle: " + gpage.status.idle + " (it starts when the gaze is used)"
+                             : gpage.status.ft_gaze ? "running" : "running, eye tracker reader starting")
                           : backend.gazeServiceInstalled ? "not running (frametop-gaze.service, starts with SteamVR)"
                           : "not installed: run gaze/run.sh install in the Frametop folder, in a terminal"
                     color: backend.gazeServiceRunning ? Kirigami.Theme.textColor : Kirigami.Theme.negativeTextColor