Cluster menu items by a gap, as Expressive does

Plan step 22, actions.md § Missing (Grouped menu layout by gap): M3
Expressive's "Grouped" layout separates clusters with a gap rather than a
divider, and `<x-menu-group>` only had the labelled form.

`<x-menu-group gap>` holds its items in a box 2px apart
(SegmentedMenuTokens.SegmentedGap) whose ends round like a list's, and
stands 8px off its neighbours — the same 8px the separator keeps around
its line. `label` is now optional, so a cluster can be a gap alone. The
header says when to reach for which: the divider first, and always in a
menu long enough to scroll, where M3 says gaps are unsupported.

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

resources/views/components/menu-group.blade.php

@@ -1,9 +1,48 @@
-{{-- A labelled group of items in an `<x-menu>`: "Sort by", "Share with". --}}
+{{-- A group of items in an `<x-menu>`, labelled ("Sort by", "Share with"), set apart by a gap, or
+     both.
 
-@props(['label'])
+     M3 Expressive gives a menu two ways to break its items into clusters, and they are not
+     interchangeable:
 
-<div role="group" aria-label="{{ $label }}" {{ $attributes->class('py-1 first:pt-0 last:pb-0') }}>
-    <div aria-hidden="true" class="px-4 pt-2 pb-1 type-label-lg text-on-surface-variant">{{ $label }}</div>
+       - `<x-menu-separator />`, a line. M3: "dividers are more subtle and are the right choice for
+         scrollable menus or text-field dropdowns", and "on web, use dividers to separate items".
+         The default answer, and the only one for a menu long enough to scroll.
+       - `<x-menu-group gap>`, the Expressive "Grouped" layout: no line, a gap. M3: "gaps are the
+         more expressive way to separate item clusters" — but "limit to one or two gaps per menu",
+         "don't vary gap size", and "never use gaps in a scrollable menu" (unsupported).
 
-    {{ $slot }}
+     A gapped cluster sets its items 2px apart (SegmentedMenuTokens.SegmentedGap = 2dp) and holds
+     them in a box of their own, so the two ends of the cluster round the way the ends of a whole
+     list round and each cluster reads as one block. Clusters stand 8px apart, the same 8px a
+     separator keeps above and below its line, so a menu is the same height whichever it uses.
+     SegmentedMenuTokens' own GroupShape is 8dp where the library's list ends are 12dp; the
+     library's shape wins, so a cluster's ends and a list's ends match. --}}
+
+@props([
+    'label' => null,
+    'gap' => false,
+])
+
+@php
+    $attributes = $attributes
+        ->class([
+            'py-1 first:pt-0 last:pb-0' => ! $gap,
+            'not-first:mt-2' => $gap,
+        ])
+        ->merge(array_filter([
+            'role' => 'group',
+            'aria-label' => $label,
+        ], fn ($value): bool => filled($value)));
+@endphp
+
+<div {{ $attributes }}>
+    @if (filled($label))
+        <div aria-hidden="true" class="px-4 pt-2 pb-1 type-label-lg text-on-surface-variant">{{ $label }}</div>
+    @endif
+
+    @if ($gap)
+        <div class="space-y-0.5">{{ $slot }}</div>
+    @else
+        {{ $slot }}
+    @endif
 </div>