feat: add SwiftUI app shell

Replace the command-line entry point with a windowed SwiftUI app
showing live dongle status, a controller placeholder, and a pair button.
The app runs as a regular foreground app even when launched directly
from the build directory.

Co-Authored-By: deepseek (deepseek/deepseek-v4-pro-0813): built SwiftUI app shell

CMakeLists.txt

@@ -6,7 +6,7 @@ if(NOT CMAKE_GENERATOR MATCHES "^(Ninja|Xcode)$")
 endif()
 
 cmake_minimum_required(VERSION 3.21)
-project(xone_macos VERSION 0.1.1 LANGUAGES CXX Swift)
+project(xone_macos VERSION 0.1.2 LANGUAGES CXX Swift)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 

src/app/main.swift

@@ -1,13 +1,91 @@
-// xone_macos — macOS app entry point (Swift)
-// TODO(phase 5): device discovery, pairing UI, status display, menubar icon.
+// xone_macos — macOS app entry point (SwiftUI)
+// TODO(phase 5): device discovery (IOKit notifications), pairing UI,
+// status display, preferences, menubar icon.
 
-import Foundation
+import AppKit
+import Combine
+import SwiftUI
 
-let version = String(cString: xone_version())
-print("xone_macos \(version)")
+struct XoneApp: App {
+    @NSApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate
 
-if xone_dongle_present() {
-    print("Xbox Wireless Dongle detected")
-} else {
-    print("No Xbox Wireless Dongle detected (plug in the dongle and retry)")
+    var body: some Scene {
+        WindowGroup {
+            ContentView()
+        }
+    }
 }
+final class AppDelegate: NSObject, NSApplicationDelegate {
+    func applicationDidFinishLaunching(_ notification: Notification) {
+        // Present as a regular app (foreground window) even when launched
+        // directly from the build directory instead of an .app bundle.
+        NSApp.setActivationPolicy(.regular)
+        NSApp.activate(ignoringOtherApps: true)
+    }
+}
+
+struct ContentView: View {
+    @State private var donglePresent = false
+
+    private let timer = Timer.publish(every: 1.0, on: .main, in: .common)
+        .autoconnect()
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 16) {
+            HStack(spacing: 8) {
+                Image(systemName: "gamecontroller.fill")
+                    .font(.largeTitle)
+                Text("xone_macos")
+                    .font(.title)
+                    .bold()
+            }
+
+            statusView
+
+            Divider()
+
+            controllersView
+
+            HStack {
+                Button("Pair Controller") {
+                    // TODO(phase 5): pairing UI (LED blink + controller press)
+                }
+                .disabled(!donglePresent)
+
+                Spacer()
+
+                Text("v\(String(cString: xone_version()))")
+                    .foregroundStyle(.secondary)
+            }
+        }
+        .padding(24)
+        .frame(width: 420)
+        .frame(minHeight: 320)
+        .onReceive(timer) { _ in
+            donglePresent = xone_dongle_present()
+        }
+    }
+
+    private var statusView: some View {
+        HStack(spacing: 8) {
+            Circle()
+                .fill(donglePresent ? Color.green : Color.red)
+                .frame(width: 10, height: 10)
+            Text(donglePresent ? "Dongle connected" : "No dongle detected")
+                .font(.headline)
+        }
+    }
+
+    private var controllersView: some View {
+        VStack(alignment: .leading, spacing: 8) {
+            Text("Controllers")
+                .font(.headline)
+            Text("No controllers connected.")
+                .foregroundStyle(.secondary)
+        }
+    }
+}
+
+// Entry point: SwiftUI App provides a static main() (top-level code lives in
+// main.swift, which CMake's Swift driver expects for executables).
+XoneApp.main()