feat: options dialog cleanup, menu/tree styling, light theme contrast

- Remove dead "Safe Mode" option, rename title case to "Uppercase menu items"
- Options tree: icons, themed hover/selection, mouse tracking (matches workspace tree)
- Tree item row padding (+4px) via MenuBarStyle CT_ItemViewItem for all trees
- Titlebar grows 2px when icon shown
- Menu popups: custom separator drawing, opaque background fill, flat hover highlight
- Menu bar/popup hover uses accent color (QPalette::Highlight) instead of grey
- Light theme: bump textMuted/textFaint contrast
- Dock grip widget for workspace and scanner docks

src/mainwindow.h

@@ -24,6 +24,7 @@ namespace rcx {
 
 class McpBridge;
 class ShimmerLabel;
+class DockGripWidget;
 
 class MainWindow : public QMainWindow {
     Q_OBJECT
@@ -158,6 +159,7 @@ private:
     QLineEdit*            m_workspaceSearch = nullptr;
     QLabel*               m_dockTitleLabel  = nullptr;
     QToolButton*          m_dockCloseBtn    = nullptr;
+    DockGripWidget*       m_dockGrip        = nullptr;
     void createWorkspaceDock();
     void rebuildWorkspaceModel();
     void updateBorderColor(const QColor& color);
@@ -167,6 +169,7 @@ private:
     ScannerPanel*         m_scannerPanel     = nullptr;
     QLabel*               m_scanDockTitle    = nullptr;
     QToolButton*          m_scanDockCloseBtn = nullptr;
+    DockGripWidget*       m_scanDockGrip     = nullptr;
     void createScannerDock();
 
 protected: