Draw the menu separator without Tailwind

The separator renders data-md-menu-separator and takes its 1px line,
8px block margin and 16px inset from menu-separator.css in
material.components (plan step 36, actions).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

resources/css/components.css

@@ -20,6 +20,7 @@
 @import './components/button-group.css';
 @import './components/split-button.css';
 @import './components/fab.css';
+@import './components/menu-separator.css';
 
 /* Inputs, selection and data */
 @import './components/form.css';