feat: reflect Low Power Mode in the menu bar battery icon

Stasis/StatusBarManager.swift

@@ -49,6 +49,7 @@ struct StatusBarContentView: View {
         BatteryIndicatorView(
             batteryLevel: viewModel.displayPercentage,
             chargingMode: viewModel.chargingMode,
+            isLowPowerModeEnabled: viewModel.isLowPowerModeEnabled,
             showPercentage: showPercentage,
             showState: showState
         )

Stasis/ViewModels/MenuViewModel.swift

@@ -28,6 +28,7 @@ class MenuViewModel {
     var systemPower: Double = 0
     var powerSource: PowerSource = .battery
     var isCharging: Bool = false
+    var isLowPowerModeEnabled: Bool = false
 
     var chargeLimitOverrideActive: Bool { chargeManager.chargeLimitOverrideActive }
     var forceDischargeActive: Bool { chargeManager.forceDischargeActive }
@@ -37,13 +38,15 @@ class MenuViewModel {
     private var metricsObservation: Task<Void, Never>?
     private var settingsObservation: Task<Void, Never>?
     private var uptimeTask: Task<Void, Never>?
+    private var powerModeObservation: Task<Void, Never>?
 
     init(batteryService: BatteryService, chargeManager: ChargeManager) {
         self.batteryService = batteryService
         self.chargeManager = chargeManager
         self.bootTimestamp = SystemService.bootTimestamp()
         startObservingMetrics()
         startObservingSettings()
+        startObservingPowerMode()
     }
 
     private func startObservingMetrics() {
@@ -80,6 +83,20 @@ class MenuViewModel {
         }
     }
 
+    private func startObservingPowerMode() {
+        isLowPowerModeEnabled = ProcessInfo.processInfo.isLowPowerModeEnabled
+
+        powerModeObservation = Task { [weak self] in
+            let notifications = NotificationCenter.default.notifications(
+                named: .NSProcessInfoPowerStateDidChange,
+                object: ProcessInfo.processInfo
+            )
+            for await _ in notifications {
+                self?.isLowPowerModeEnabled = ProcessInfo.processInfo.isLowPowerModeEnabled
+            }
+        }
+    }
+
     func toggleChargeLimitOverride() {
         chargeManager.toggleChargeLimitOverride()
     }
@@ -217,6 +234,7 @@ class MenuViewModel {
             metricsObservation?.cancel()
             settingsObservation?.cancel()
             uptimeTask?.cancel()
+            powerModeObservation?.cancel()
         }
     }
 }

Stasis/Views/BatteryIndicatorView.swift

@@ -3,13 +3,18 @@ import SwiftUI
 struct BatteryIndicatorView: View {
     let batteryLevel: Int
     let chargingMode: ChargingMode
+    var isLowPowerModeEnabled: Bool = false
     var showPercentage: Bool = false
     var showState: Bool = false
 
     private var fillColor: Color {
+        // Critical level takes priority over Low Power Mode.
         if showState && batteryLevel <= 10 {
             return .red
         }
+        if isLowPowerModeEnabled {
+            return .yellow
+        }
         return .primary
     }
 
@@ -118,6 +123,28 @@ struct BatteryTerminal: View {
                 )
             }
         }
+
+        Divider()
+
+        Text("Low Power Mode (yellow; critical red takes priority)")
+            .font(.caption)
+            .foregroundStyle(.secondary)
+
+        ForEach([100, 50, 10, 5], id: \.self) { level in
+            HStack(spacing: 20) {
+                BatteryIndicatorView(
+                    batteryLevel: level,
+                    chargingMode: .discharging,
+                    isLowPowerModeEnabled: true,
+                    showState: true
+                )
+                BatteryIndicatorView(
+                    batteryLevel: level,
+                    chargingMode: .charging,
+                    isLowPowerModeEnabled: true
+                )
+            }
+        }
     }
     .padding()
     .background(Color(NSColor.windowBackgroundColor))