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/windows/backends/sway/SwayIpcClient.hpp

@@ -0,0 +1,71 @@
+#pragma once
+
+#include <QByteArray>
+#include <QJsonDocument>
+#include <QLocalSocket>
+#include <QObject>
+#include <QStringList>
+#include <QVector>
+
+class SwayIpcClient : public QObject
+{
+    Q_OBJECT
+
+public:
+    enum MessageType : quint32 {
+        RunCommand = 0,
+        GetWorkspaces = 1,
+        Subscribe = 2,
+        GetOutputs = 3,
+        GetTree = 4,
+        GetMarks = 5,
+        GetVersion = 7
+    };
+
+    enum EventType : quint32 {
+        WorkspaceEvent = 0x80000000u,
+        OutputEvent = 0x80000001u,
+        WindowEvent = 0x80000003u,
+        BindingEvent = 0x80000005u,
+        ShutdownEvent = 0x80000006u
+    };
+
+    explicit SwayIpcClient(QObject *parent = nullptr);
+    ~SwayIpcClient() override;
+
+    bool connectToSway();
+    void disconnectFromSway();
+    bool isConnected() const;
+
+    QJsonDocument request(quint32 type, const QByteArray &payload = {});
+    bool subscribe(const QStringList &events);
+
+    static QString socketPath();
+
+signals:
+    void connectedChanged();
+    void disconnected();
+    void eventReceived(quint32 type, const QJsonDocument &payload);
+
+private:
+    struct Message {
+        quint32 type = 0;
+        QByteArray payload;
+    };
+
+    bool writeMessage(QLocalSocket *socket, quint32 type, const QByteArray &payload);
+    bool readMessage(QLocalSocket *socket, Message *message, int timeoutMs);
+    void appendIncoming(QLocalSocket *socket, QByteArray *buffer);
+    bool takeMessage(QByteArray *buffer, Message *message);
+    void processEventSocket();
+    void flushPendingEvents();
+    void handleCommandDisconnected();
+    void handleEventDisconnected();
+
+    QLocalSocket *m_command = nullptr;
+    QLocalSocket *m_event = nullptr;
+    QByteArray m_eventBuffer;
+    QVector<Message> m_pendingEvents;
+    int m_inRequest = 0;
+    bool m_connected = false;
+};