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>

shell/plugins/services/nightlight/NightlightModel.js

@@ -0,0 +1,20 @@
+// Temperatures below the identity point count as night light. Keep in sync
+// with bin/omarchy-toggle-nightlight, which applies the same threshold.
+var IDENTITY_TEMPERATURE = 6000
+
+function temperatureFromOutput(output) {
+  var match = String(output === undefined || output === null ? "" : output).match(/[0-9]+/)
+  return match ? Number(match[0]) : null
+}
+
+function isNightlight(temperature) {
+  return temperature !== null && temperature !== undefined && temperature < IDENTITY_TEMPERATURE
+}
+
+if (typeof module !== "undefined") {
+  module.exports = {
+    IDENTITY_TEMPERATURE: IDENTITY_TEMPERATURE,
+    temperatureFromOutput: temperatureFromOutput,
+    isNightlight: isNightlight
+  }
+}