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

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

LanMountainDesktop.Launcher/Startup/HostActivationPolicy.cs

@@ -0,0 +1,50 @@
+using LanMountainDesktop.Shared.Contracts.Launcher;
+using LanMountainDesktop.Shared.IPC.Abstractions.Services;
+
+namespace LanMountainDesktop.Launcher.Startup;
+
+internal static class HostActivationPolicy
+{
+    internal static bool ShouldProbeExistingHostBeforeLaunch(CommandContext context)
+    {
+        if (!string.Equals(context.Command, "launch", StringComparison.OrdinalIgnoreCase))
+        {
+            return false;
+        }
+
+        if (context.IsPreviewCommand || context.IsMaintenanceCommand)
+        {
+            return false;
+        }
+
+        return !string.Equals(context.LaunchSource, "restart", StringComparison.OrdinalIgnoreCase);
+    }
+
+    internal static bool IsExistingHostReadyForLauncherDecision(PublicShellStatus? status) =>
+        status is { PublicIpcReady: true, ProcessId: > 0 };
+
+    internal static bool IsRecoverableActivationFailure(PublicShellActivationResult activation)
+    {
+        if (activation.Accepted)
+        {
+            return false;
+        }
+
+        if (string.Equals(activation.Code, "shutdown_in_progress", StringComparison.OrdinalIgnoreCase))
+        {
+            return false;
+        }
+
+        return activation.Status.PublicIpcReady &&
+               (!activation.Status.MainWindowOpened ||
+                !activation.Status.DesktopVisible ||
+                string.Equals(activation.Code, "shell_not_ready", StringComparison.OrdinalIgnoreCase) ||
+                string.Equals(activation.Code, "startup_pending", StringComparison.OrdinalIgnoreCase));
+    }
+
+    internal static bool IsSuccessfulActivationExitCode(int exitCode) =>
+        exitCode == HostExitCodes.SecondaryActivationSucceeded;
+
+    internal static bool IsFailedActivationExitCode(int exitCode) =>
+        exitCode is HostExitCodes.SecondaryActivationFailed or HostExitCodes.RestartLockNotAcquired;
+}