Rewrite the divider without Tailwind

Plan step 36 (containment group): <x-divider> moves its class lists
into resources/css/components/divider.css, keyed on data-md-divider,
data-md-orientation, data-md-inset/middle and data-md-divider-heading/
-text for the subheader form (DividerTokens.kt; docs/reference/m3
§ Divider). Imported from the Containment block of components.css.

Hooks renamed: none of divider's own (it had no data-* hooks before),
but its rendered attribute order moved data-md-* ahead of role/aria-*,
which ToolbarTest.php's regex for a toolbar's vertical divider depended
on; fixed in the same commit. form.css picks up the @import './divider.css'
its TODO(step 36) marker was waiting on, since form.blade.php renders
<x-divider> and divider.css now carries the material.components layer.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

resources/css/components/form.css

@@ -17,7 +17,7 @@
 
 @layer material.reset, material.tokens, material.base, material.layout, material.components, material.text, material.visibility;
 
-/* TODO(step 36): @import './divider.css' once <x-divider> leaves Tailwind (containment stream). */
+@import './divider.css';
 
 @layer material.components {
     [data-md-form] {