fix(launcher): extract startup subsystem and harden IPC detection

Co-authored-by: Cursor <cursoragent@cursor.com>

LanMountainDesktop.Tests/StartupSuccessTrackerTests.cs

@@ -0,0 +1,56 @@
+using LanMountainDesktop.Launcher;
+using LanMountainDesktop.Launcher.Startup;
+using LanMountainDesktop.Shared.Contracts.Launcher;
+using LanMountainDesktop.Shared.IPC.Abstractions.Services;
+using Xunit;
+
+namespace LanMountainDesktop.Tests;
+
+public sealed class StartupSuccessTrackerTests
+{
+    [Fact]
+    public void TryResolve_DesktopVisibleStage_SucceedsForForegroundLaunch()
+    {
+        var tracker = new StartupSuccessTracker(CreateContext("normal"));
+        Assert.True(tracker.TryResolve(StartupStage.DesktopVisible, out var state));
+        Assert.Equal("ok", state.Code);
+    }
+
+    [Fact]
+    public void TryResolve_ShellStatusWithMainWindowOpened_Succeeds()
+    {
+        var tracker = new StartupSuccessTracker(CreateContext("normal"));
+        var status = new PublicShellStatus(
+            ProcessId: 1234,
+            StartedAtUtc: DateTimeOffset.UtcNow,
+            LaunchSource: "normal",
+            ShellState: "opened",
+            MainWindowCreated: true,
+            MainWindowVisible: false,
+            MainWindowOpened: true,
+            DesktopVisible: false,
+            PublicIpcReady: true,
+            Tray: new PublicTrayStatus("Unavailable", false, false, false, false, 0),
+            Taskbar: new PublicTaskbarStatus(false, true, false, false, false, true));
+
+        Assert.True(tracker.TryResolve(status, out var state));
+        Assert.Equal(StartupStage.Ready, state.Stage);
+    }
+
+    [Fact]
+    public void TryResolve_RestartTrayPolicy_RequiresTrayAndBackground()
+    {
+        var tracker = new StartupSuccessTracker(CreateContext("restart", "--restart-presentation", "tray"));
+        Assert.False(tracker.TryResolve(StartupStage.TrayReady, out _));
+        Assert.True(tracker.TryResolve(StartupStage.BackgroundReady, out _));
+        Assert.True(tracker.TryResolve(StartupStage.TrayReady, out var final));
+        Assert.Equal("background_ready", final.Code);
+    }
+
+    private static CommandContext CreateContext(string launchSource, params string[] extraArgs)
+    {
+        var args = new List<string> { "launch", "--launch-source", launchSource };
+        args.AddRange(extraArgs);
+        return CommandContext.FromArgs(args.ToArray());
+    }
+}