Let a docked toolbar carry a FAB

Plan step 25 (navigation Missing): M3's toolbar configuration table lists
"With FAB" for both toolbars, but the `fab` slot was gated to the floating one.
A docked toolbar now takes it at its end, inside the toolbar where the arrow
keys reach it; its controls gather at the start, and the FAB rests flat on the
bar — elevation 0 for a FAB nested in another component, as Compose's
bottomAppBarFabElevation is.

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

resources/views/showcase/sections/bars.blade.php

@@ -73,6 +73,16 @@
                         <x-button icon="delete" tooltip="Delete" />
                     </x-toolbar>
                 </div>
+
+                <div class="w-full overflow-hidden rounded-corner-lg border border-outline-variant">
+                    <x-toolbar variant="docked" label="Editing">
+                        <x-button icon="check_box" tooltip="Select" />
+                        <x-button icon="brush" tooltip="Draw" />
+                        <x-button icon="mic" tooltip="Record" />
+                        <x-button icon="image" tooltip="Add image" />
+                        <x-slot:fab><x-fab icon="add" tooltip="New note" color="secondary" /></x-slot:fab>
+                    </x-toolbar>
+                </div>
             </div>
             BLADE,
         'Primary tabs' => <<<'BLADE'