Draw the menu without Tailwind

<x-menu> renders data-md-menu with data-md-sheet-at-compact, and its
popover data-md-menu-popover with data-md-position and data-md-vibrant;
menu.css caps a long menu at 288px so it scrolls instead of running
off the top layer (ACT-04) and ties the open/close transition to the
trigger's corner (ACT-26), restyles a submenu to open in place inside
a sheet-at-compact sheet, and still carries the dropdown a select's
picker and a searchable choices field draw, so select.css and
choices.css finish their step-36 TODO import. actions.css sheds the
state-transition-fast and popover-transition utilities menu-item and
menu no longer use; state-transition-default and [data-fab-menu]
stay for fab-menu's own rewrite.

data-menu, data-menu-filter, data-menu-sheet, data-menu-empty,
data-sheet-at-compact, data-vibrant and data-active are renamed to
data-md-*, also in menu.js, split-button.css (which renders a
<x-menu> and now imports its stylesheet) and AppBarTest's overflow
menu (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/split-button.css

@@ -21,6 +21,7 @@
 @layer material.reset, material.tokens, material.base, material.layout, material.components, material.text, material.visibility;
 
 @import './button.css';
+@import './menu.css';
 
 @layer material.components {
     [data-md-split-button] {