Remember power profile choices per power source across reboots

Explicit profile selections from the power panel or menu are now saved
under an ac/battery key in ~/.local/state/omarchy/powerprofiles and
reapplied on boot and on plug/unplug. Only successful, user-made
selections are persisted, so the performance/balanced defaults still
apply when nothing has been chosen.

All entry points key off the same power signal, UPower's OnBattery:
the shell reads it natively and omarchy-powerprofiles-set autodetect
queries it via busctl. This replaces the sysfs online checks, which
disagreed with the shell on desktops without power_supply entries and
lagged behind plug events on some USB-C laptops.

Plug/unplug switching moves from the udev rule into the shell's battery
service, which already receives UPower's debounced state changes, so
the udev rule and its settle-sleep workaround are gone.

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

shell/plugins/services/battery/Service.qml

@@ -11,6 +11,7 @@ Item {
   property string omarchyPath: Quickshell.env("OMARCHY_PATH")
 
   readonly property int batteryThreshold: 10
+  property string pendingPowerSource: ""
 
   PersistentProperties {
     id: persisted
@@ -41,8 +42,24 @@ Item {
     warningProcess.running = true
   }
 
+  function applyPowerProfile() {
+    pendingPowerSource = UPower.onBattery ? "battery" : "ac"
+    if (!powerProfileProcess.running) runPendingPowerProfile()
+  }
+
+  function runPendingPowerProfile() {
+    powerProfileProcess.command = ["omarchy-powerprofiles-set", pendingPowerSource]
+    pendingPowerSource = ""
+    powerProfileProcess.running = true
+  }
+
   Process { id: warningProcess }
 
+  Process {
+    id: powerProfileProcess
+    onExited: if (root.pendingPowerSource !== "") root.runPendingPowerProfile()
+  }
+
   Timer {
     interval: 30000
     running: true
@@ -53,6 +70,9 @@ Item {
 
   Connections {
     target: UPower
-    function onOnBatteryChanged() { root.checkBattery() }
+    function onOnBatteryChanged() {
+      root.checkBattery()
+      root.applyPowerProfile()
+    }
   }
 }