Move Night Light onto a first-party nightlight service

Same treatment as Stay Awake: the indicator polled the toggle CLI over
a Process with a timer to paper over the race after clicking, and the
CLI ended by asking the shell to refresh every indicator over IPC. A new
omarchy.nightlight service owns hyprsunset instead - it probes the
temperature on startup, applies changes itself for in-shell toggles, and
answers on the nightlight IPC target. The indicator becomes a plain
binding. The CLI still drives hyprctl directly so keybindings, the menu,
and ssh work without the shell, but now just nudges the service to
re-probe since hyprsunset has no state file to watch.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/shell.d/fixtures/indicator-contract/shell.qml

@@ -33,11 +33,20 @@ ShellRoot {
     }
   }
 
+  QtObject {
+    id: nightlightService
+    property bool enabled: false
+    function setNightlight(value) {
+      enabled = !!value
+    }
+  }
+
   QtObject {
     id: mockShell
     function firstPartyServiceFor(id) {
       if (id === "omarchy.notifications") return notificationService
       if (id === "omarchy.idle") return idleService
+      if (id === "omarchy.nightlight") return nightlightService
       return null
     }
   }
@@ -175,7 +184,7 @@ ShellRoot {
         nightLight.moduleName = "NightLight"
         root.injectBar(nightLight)
         nightLight.triggerPress(Qt.LeftButton)
-        root.assertTrue(root.commandCount("omarchy-toggle-nightlight") === 1, "Night Light left click runs toggle command")
+        root.assertTrue(nightlightService.enabled === true, "Night Light left click toggles the nightlight service")
       }
 
       var screenRecording = root.createIndicator("ScreenRecording")