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.hpp

@@ -20,7 +20,10 @@ class ApplicationService : public QObject
 
 public:
     explicit ApplicationService(QObject *parent = nullptr);
+    ~ApplicationService() override;
+
     static ApplicationService *create(QQmlEngine *engine, QJSEngine *scriptEngine);
+    static ApplicationService *instance();
 
     ApplicationModel *model() const;
     ApplicationFilterModel *filteredModel() const;
@@ -30,6 +33,8 @@ public:
     int count() const;
 
     Q_INVOKABLE bool launch(const QString &desktopId) const;
+    Q_INVOKABLE QString displayNameForWindow(const QString &appId, const QString &windowClass) const;
+    Q_INVOKABLE QString iconNameForWindow(const QString &appId, const QString &windowClass) const;
     Q_INVOKABLE void refresh();
 
 signals: