Add Nebula.Windows with Sway IPC backend

Introduces a new `core/windows` module (`Nebula.Windows`) with `WindowService`, window/workspace models, and a Sway IPC backend for live window tracking and control (focus, close, move/resize, snap, maximize/restore, minimize, workspace switch). The desktop shell now links this module, uses compositor focus for top-bar active app text, and adds an Open Windows section in the launcher with focus/close actions.

Also updates application metadata handling to parse `StartupWMClass` and map window `app_id`/class to friendly names and icons, and revises Sway config/docs for the new floating-first Desktop 0.2 behavior with temporary compositor-provided decorations.

core/applications/ApplicationService.cpp

@@ -7,13 +7,21 @@
 #include <QFileInfo>
 #include <QSet>
 #include <QVector>
+#include <QtGlobal>
 #include <utility>
 
+namespace {
+ApplicationService *s_instance = nullptr;
+}
+
 ApplicationService::ApplicationService(QObject *parent)
     : QObject(parent)
     , m_model(new ApplicationModel(this))
     , m_filtered(new ApplicationFilterModel(this))
 {
+    if (!s_instance)
+        s_instance = this;
+
     m_filtered->setSourceModel(m_model);
     m_filtered->setSortRole(ApplicationModel::NameRole);
     m_filtered->sort(0, Qt::AscendingOrder);
@@ -24,6 +32,17 @@ ApplicationService::ApplicationService(QObject *parent)
     refresh();
 }
 
+ApplicationService::~ApplicationService()
+{
+    if (s_instance == this)
+        s_instance = nullptr;
+}
+
+ApplicationService *ApplicationService::instance()
+{
+    return s_instance;
+}
+
 ApplicationService *ApplicationService::create(QQmlEngine *engine, QJSEngine *)
 {
     auto *service = new ApplicationService(engine);
@@ -66,6 +85,22 @@ bool ApplicationService::launch(const QString &desktopId) const
     return entry->launch();
 }
 
+QString ApplicationService::displayNameForWindow(const QString &appId, const QString &windowClass) const
+{
+    const DesktopEntry *entry = m_model->entryMatchingWindow(appId, windowClass);
+    if (entry && !entry->name.isEmpty())
+        return entry->name;
+    return {};
+}
+
+QString ApplicationService::iconNameForWindow(const QString &appId, const QString &windowClass) const
+{
+    const DesktopEntry *entry = m_model->entryMatchingWindow(appId, windowClass);
+    if (entry)
+        return entry->icon;
+    return {};
+}
+
 void ApplicationService::refresh()
 {
     QVector<DesktopEntry> entries;