Fix Qt compatibility and VM script docs

Updates desktop shell and application code for cross-Qt compatibility: uses begin/endFilterChange for Qt 6.10+, gates LayerShell usage to Qt < 6.5, and adds include handling for generated QML type registration files so nebula-shell builds reliably. Also fixes qInfo size formatting casts and updates README commands to invoke run-sway-vm.sh via `sh` for more portable execution.

core/applications/ApplicationService.cpp

@@ -73,7 +73,7 @@ void ApplicationService::refresh()
 
     const QStringList directories = applicationDirectories();
     qInfo("nebula: scanning %d application director%s",
-          directories.size(),
+          int(directories.size()),
           directories.size() == 1 ? "y" : "ies");
 
     for (const QString &directory : directories) {
@@ -103,7 +103,7 @@ void ApplicationService::refresh()
     }
 
     qInfo("nebula: discovered %d launcher application%s",
-          entries.size(),
+          int(entries.size()),
           entries.size() == 1 ? "" : "s");
     m_model->setEntries(std::move(entries));
 }