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

tests/Feature/Components/AppBarTest.php

@@ -69,6 +69,27 @@ it('draws floating and docked toolbars', function () {
         ->not->toContain('data-toolbar-group');
 });
 
+it('sets a FAB at the end of a docked toolbar, resting flat on it', function () {
+    $html = (string) $this->blade(<<<'BLADE'
+        <x-toolbar variant="docked" label="Editing">
+            <button>Draw</button>
+            <x-slot:fab><button>+</button></x-slot:fab>
+        </x-toolbar>
+        BLADE);
+
+    expect($html)
+        // Inside the toolbar, after its controls, where the arrow keys reach it too.
+        ->toMatch('/role="toolbar".*<button>Draw<\/button>\s*<div data-toolbar-fab><button>\+<\/button><\/div>\s*<\/div>/s')
+        ->not->toContain('data-toolbar-group')
+        ->and((string) $this->blade('<x-toolbar variant="docked"><button>Draw</button></x-toolbar>'))
+        ->not->toContain('data-toolbar-fab');
+
+    expect(file_get_contents(__DIR__.'/../../../resources/css/components/toolbar.css'))
+        ->toMatch('/\[data-toolbar-fab\] \{\s+display: flex;\s+margin-inline-start: auto;/')
+        // A nested FAB rests at elevation 0.
+        ->toMatch('/\[data-toolbar-fab\] \[data-fab\],\s+\[data-toolbar-fab\] \[data-fab\]:hover \{\s+box-shadow: none;/');
+});
+
 it('centres a headline on a three-column row and curves the search container', function () {
     $css = file_get_contents(__DIR__.'/../../../resources/css/components/app-bar.css');