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/ApplicationModel.cpp

@@ -91,3 +91,49 @@ const DesktopEntry *ApplicationModel::entryById(const QString &desktopId) const
     }
     return nullptr;
 }
+
+const DesktopEntry *ApplicationModel::entryMatchingWindow(const QString &appId, const QString &windowClass) const
+{
+    auto stem = [](QString value) {
+        if (value.endsWith(QLatin1String(".desktop"), Qt::CaseInsensitive))
+            value.chop(8);
+        return value.toLower();
+    };
+
+    const QString app = stem(appId);
+    const QString cls = stem(windowClass);
+    const QString appLast = app.contains(QLatin1Char('.')) ? app.section(QLatin1Char('.'), -1) : app;
+    const QString classLast = cls.contains(QLatin1Char('.')) ? cls.section(QLatin1Char('.'), -1) : cls;
+
+    const DesktopEntry *wmClassMatch = nullptr;
+    const DesktopEntry *lastComponentMatch = nullptr;
+
+    for (const DesktopEntry &entry : m_entries) {
+        const QString id = stem(entry.desktopId);
+        if (!app.isEmpty() && id == app)
+            return &entry;
+        if (!cls.isEmpty() && id == cls)
+            return &entry;
+
+        if (!entry.startupWmClass.isEmpty()) {
+            const QString wm = stem(entry.startupWmClass);
+            if ((!app.isEmpty() && wm == app) || (!cls.isEmpty() && wm == cls)
+                || (!appLast.isEmpty() && wm == appLast) || (!classLast.isEmpty() && wm == classLast)) {
+                if (!wmClassMatch)
+                    wmClassMatch = &entry;
+            }
+        }
+
+        if (!lastComponentMatch) {
+            const QString idLast = id.contains(QLatin1Char('.')) ? id.section(QLatin1Char('.'), -1) : id;
+            if (appLast.size() >= 3 && (id == appLast || idLast == appLast))
+                lastComponentMatch = &entry;
+            else if (classLast.size() >= 3 && (id == classLast || idLast == classLast))
+                lastComponentMatch = &entry;
+        }
+    }
+
+    if (wmClassMatch)
+        return wmClassMatch;
+    return lastComponentMatch;
+}