Fill the FAB and icon-button glyphs, and cut small ones at 20

M3 asks a FAB's icon and a default (non-toggle) icon button's icon to be filled,
never outlined; the toggle half of that rule was already right, so only the
`$selected === null` case changed. Every glyph these components draw at 20px now
passes `optical="20"` for the cut M3 draws at that size — button xs/sm, group,
menu item, the alert, snackbar and FAB-menu close buttons, the stat's icon.
Plan step 18, actions.md ACT-14, ACT-15.

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

resources/views/components/group.blade.php

@@ -63,6 +63,8 @@
         : 'mt-1 type-body-sm text-on-surface-variant';
 
     $iconSize = ['xs' => 'size-5', 'sm' => 'size-5', 'md' => 'size-6', 'lg' => 'size-8', 'xl' => 'size-10'][$size];
+    // A 20px glyph comes from M3's 20px cut, which is drawn for that size rather than scaled to it.
+    $optical = $iconSize === 'size-5' ? '20' : '24';
 
     $colours = match ($variant) {
         'filled' => 'bg-surface-container text-on-surface-variant has-checked:bg-primary has-checked:text-on-primary',
@@ -98,7 +100,7 @@
                 />
 
                 @if (filled(data_get($option, $optionIcon)))
-                    <x-livewire-material::icon :name="data_get($option, $optionIcon)" :class="$iconSize" />
+                    <x-livewire-material::icon :name="data_get($option, $optionIcon)" :optical="$optical" :class="$iconSize" />
                 @endif
 
                 <span class="truncate">{{ data_get($option, $optionLabel) }}</span>