feat: add inherited sessions and desktop session teardown

programs/src/desktop/main.cpp

@@ -895,6 +895,11 @@ static bool existing_desktop_running() {
 }
 
 extern "C" void _start() {
+    // External applications and all of their descendants inherit this stable
+    // desktop-session ID. login.elf uses it to tear down the complete session
+    // after Log Out, Shutdown, or Reboot returns control to the supervisor.
+    montauk::setsession();
+
     if (existing_desktop_running()) {
         gui::dialogs::message_box(
             "Desktop Already Running",