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

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

LanMountainDesktop.Tests/HostActivationPolicyTests.cs

@@ -0,0 +1,46 @@
+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 HostActivationPolicyTests
+{
+    [Theory]
+    [InlineData("launch", "normal", true)]
+    [InlineData("launch", "restart", false)]
+    [InlineData("apply-update", "normal", false)]
+    public void ShouldProbeExistingHostBeforeLaunch_RespectsLaunchSource(
+        string command,
+        string launchSource,
+        bool expected)
+    {
+        var context = CommandContext.FromArgs([command, "--launch-source", launchSource]);
+        Assert.Equal(expected, HostActivationPolicy.ShouldProbeExistingHostBeforeLaunch(context));
+    }
+
+    [Fact]
+    public void IsRecoverableActivationFailure_AllowsStartupPendingWhenIpcReady()
+    {
+        var activation = new PublicShellActivationResult(
+            false,
+            "startup_pending",
+            "pending",
+            new PublicShellStatus(
+                ProcessId: 1,
+                StartedAtUtc: DateTimeOffset.UtcNow,
+                LaunchSource: "normal",
+                ShellState: "initializing",
+                MainWindowCreated: false,
+                MainWindowVisible: false,
+                MainWindowOpened: false,
+                DesktopVisible: false,
+                PublicIpcReady: true,
+                Tray: new PublicTrayStatus("Unavailable", false, false, false, false, 0),
+                Taskbar: new PublicTaskbarStatus(false, false, false, false, false, false)));
+
+        Assert.True(HostActivationPolicy.IsRecoverableActivationFailure(activation));
+    }
+}