Add focused window controls to top bar

Introduces a new `WindowControls` component in the desktop top bar with minimize, maximize/restore, and close actions for the focused window. `WindowService` now exposes focused-window presence/maximized state plus focused-window convenience actions to support this UI.

Also extends Nebula UI with a reusable `NebulaToolTip`, keyboard/pressed-state support in `NebulaIconButton`, new window-control glyphs in `NebulaIcon`, and theme tokens for pressed/danger hover states, with CMake and README updates to register/document the new components.

core/windows/WindowService.cpp

@@ -67,6 +67,11 @@ int WindowService::windowCount() const
     return m_model->count();
 }
 
+bool WindowService::hasFocusedWindow() const
+{
+    return !m_focusedWindowId.isEmpty();
+}
+
 QString WindowService::focusedWindowId() const
 {
     return m_focusedWindowId;
@@ -87,6 +92,11 @@ QString WindowService::focusedApplicationName() const
     return m_focusedApplicationName;
 }
 
+bool WindowService::focusedWindowMaximized() const
+{
+    return m_focusedWindowMaximized;
+}
+
 bool WindowService::focusWindow(const QString &windowId)
 {
     return m_backend->focusWindow(parseWindowId(windowId));
@@ -112,6 +122,38 @@ bool WindowService::minimizeWindow(const QString &windowId)
     return m_backend->minimizeWindow(parseWindowId(windowId));
 }
 
+bool WindowService::minimizeFocusedWindow()
+{
+    if (m_focusedWindowId.isEmpty())
+        return false;
+    return minimizeWindow(m_focusedWindowId);
+}
+
+bool WindowService::toggleMaximizeFocusedWindow()
+{
+    if (m_focusedWindowId.isEmpty())
+        return false;
+
+    const bool restore = m_focusedWindowMaximized;
+    const bool ok = restore ? restoreWindow(m_focusedWindowId)
+                            : maximizeWindow(m_focusedWindowId);
+    if (!ok)
+        return false;
+
+    if (m_focusedWindowMaximized == restore) {
+        m_focusedWindowMaximized = !restore;
+        emit focusChanged();
+    }
+    return true;
+}
+
+bool WindowService::closeFocusedWindow()
+{
+    if (m_focusedWindowId.isEmpty())
+        return false;
+    return closeWindow(m_focusedWindowId);
+}
+
 bool WindowService::setWindowFloating(const QString &windowId, bool floating)
 {
     return m_backend->setWindowFloating(parseWindowId(windowId), floating);
@@ -154,6 +196,7 @@ void WindowService::syncFromBackend()
     QString title;
     QString appId;
     QString appName;
+    bool maximized = false;
 
     if (const WindowInfo *focused = m_model->windowById(focusedId)) {
         if (!focused->minimized) {
@@ -161,17 +204,20 @@ void WindowService::syncFromBackend()
             title = focused->title;
             appId = focused->appId.isEmpty() ? focused->windowClass : focused->appId;
             appName = focused->displayName;
+            maximized = focused->maximized;
         }
     }
 
     if (m_focusedWindowId != windowId
         || m_focusedWindowTitle != title
         || m_focusedApplicationId != appId
-        || m_focusedApplicationName != appName) {
+        || m_focusedApplicationName != appName
+        || m_focusedWindowMaximized != maximized) {
         m_focusedWindowId = windowId;
         m_focusedWindowTitle = title;
         m_focusedApplicationId = appId;
         m_focusedApplicationName = appName;
+        m_focusedWindowMaximized = maximized;
         emit focusChanged();
     }
 }