fix: prevent idle sleep during playback

Sources/App/SystemPlaybackControls.swift

@@ -23,6 +23,8 @@ final class SystemPlaybackControls {
     private let infoCenter = MPNowPlayingInfoCenter.default()
     private var targets: [(MPRemoteCommand, Any)] = []
     private var snapshot: Snapshot?
+    private var activity: NSObjectProtocol?
+    private var activityOptions: ProcessInfo.ActivityOptions = []
 
     init(model: PlayerModel) {
         self.model = model
@@ -75,6 +77,23 @@ final class SystemPlaybackControls {
     }
 
     func update() {
+        var options: ProcessInfo.ActivityOptions = []
+        if let model, model.fileName != nil,
+           model.state.status == PLAYER_PLAYING || model.castConnecting {
+            options = .userInitiated
+            if model.state.status == PLAYER_PLAYING, model.state.has_video,
+               model.castDevice == nil || model.castConnecting {
+                options.insert(.idleDisplaySleepDisabled)
+            }
+        }
+        if options != activityOptions {
+            // Acquire before releasing so a local/Cast handoff cannot briefly allow sleep.
+            let next = options.isEmpty ? nil :
+                ProcessInfo.processInfo.beginActivity(options: options, reason: "Playing media")
+            if let activity { ProcessInfo.processInfo.endActivity(activity) }
+            activity = next
+            activityOptions = options
+        }
         let ready = model?.fileName != nil && model?.canTogglePlayback == true
         let seekable = ready && model?.canSeek == true
         for (command, _) in targets {
@@ -117,6 +136,9 @@ final class SystemPlaybackControls {
     }
 
     func shutdown() {
+        if let activity { ProcessInfo.processInfo.endActivity(activity) }
+        activity = nil
+        activityOptions = []
         for (command, target) in targets {
             command.removeTarget(target)
             command.isEnabled = false