fix: start at launch, not when the main window appears

As a login item macOS launched Musubi without its window, so the SwiftUI
.task never ran: no outputs, no remote control after a reboot. An app
delegate now starts discovery and the coordinator in applicationDidFinishLaunching.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

App/Sources/MusubiApp.swift

@@ -1,3 +1,4 @@
+import AppKit
 import DesignSystem
 import NDIKit
 import OSLog
@@ -5,31 +6,35 @@ import SwiftUI
 
 @main
 struct MusubiApp: App {
-    @State private var sourceList = SourceListModel()
-    @State private var coordinator: Coordinator = {
-        MainActor.assumeIsolated {
-            Coordinator(settings: AppSettings(), outputs: OutputController(), audio: AudioController())
-        }
-    }()
+    @NSApplicationDelegateAdaptor private var appDelegate: AppDelegate
 
     var body: some SwiftUI.Scene {
         Window("Musubi", id: "main") {
-            ContentView(sourceList: sourceList, coordinator: coordinator)
+            ContentView(sourceList: appDelegate.sourceList, coordinator: appDelegate.coordinator)
                 .preferredColorScheme(.dark)
-                .task {
-                    sourceList.start()
-                    await coordinator.start()
-                }
         }
         .defaultSize(width: 960, height: 600)
 
         Settings {
-            SettingsView(coordinator: coordinator)
+            SettingsView(coordinator: appDelegate.coordinator)
                 .preferredColorScheme(.dark)
         }
     }
 }
 
+/// Starts discovery, outputs, audio and remote control at launch – independent of any window.
+/// As a login item macOS may launch Musubi without opening its window.
+@MainActor
+final class AppDelegate: NSObject, NSApplicationDelegate {
+    let sourceList = SourceListModel()
+    let coordinator = Coordinator(settings: AppSettings(), outputs: OutputController(), audio: AudioController())
+
+    func applicationDidFinishLaunching(_ notification: Notification) {
+        sourceList.start()
+        Task { await coordinator.start() }
+    }
+}
+
 enum Log {
     static let ndi = Logger(subsystem: "studio.zielke.musubi", category: "ndi")
     static let audio = Logger(subsystem: "studio.zielke.musubi", category: "audio")