fix: DividerWidget renders without border chrome and detach button

DividerWidget now gets a borderless panel with the dashboard background
color instead of the standard widget border. The detach button is also
skipped for dividers since they are purely decorative separators.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: HanSur94

libs/Dashboard/DashboardLayout.m

@@ -272,13 +272,22 @@ function allocatePanels(obj, hFigure, widgets, theme)
                 w = widgets{i};
                 w.ParentTheme = theme;
                 pos = obj.computePosition(w.Position);
-                hp = uipanel('Parent', obj.hCanvas, ...
-                    'Units', 'normalized', ...
-                    'Position', pos, ...
-                    'BorderType', 'line', ...
-                    'BorderWidth', theme.WidgetBorderWidth, ...
-                    'ForegroundColor', theme.WidgetBorderColor, ...
-                    'BackgroundColor', theme.WidgetBackground);
+                isDivider = isa(w, 'DividerWidget');
+                if isDivider
+                    hp = uipanel('Parent', obj.hCanvas, ...
+                        'Units', 'normalized', ...
+                        'Position', pos, ...
+                        'BorderType', 'none', ...
+                        'BackgroundColor', theme.DashboardBackground);
+                else
+                    hp = uipanel('Parent', obj.hCanvas, ...
+                        'Units', 'normalized', ...
+                        'Position', pos, ...
+                        'BorderType', 'line', ...
+                        'BorderWidth', theme.WidgetBorderWidth, ...
+                        'ForegroundColor', theme.WidgetBorderColor, ...
+                        'BackgroundColor', theme.WidgetBackground);
+                end
                 w.hPanel = hp;
                 uicontrol('Parent', hp, 'Style', 'text', 'Units', 'normalized', ...
                     'Position', [0.05 0.4 0.9 0.2], ...
@@ -308,8 +317,8 @@ function realizeWidget(obj, widget)
             if ~isempty(widget.Description)
                 obj.addInfoIcon(widget);
             end
-            % Inject detach button when DetachCallback is wired
-            if ~isempty(obj.DetachCallback)
+            % Inject detach button when DetachCallback is wired (skip for dividers)
+            if ~isempty(obj.DetachCallback) && ~isa(widget, 'DividerWidget')
                 obj.addDetachButton(widget);
             end
         end