Mark a FAB's root with data-fab

A FAB nested in another component has to be restyled from that component's
stylesheet, and its root carried no hook. Added here rather than with the rule
that needs it, so the actions stream's own use of the hook merges cleanly.
Plan: docs/plans/material-3-alignment.md, step 14 (navigation N-03).

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

resources/views/components/fab.blade.php

@@ -9,6 +9,9 @@
      `<div class="fixed end-4 bottom-4"><x-fab icon="add" tooltip="New share" /></div>`. For a
      create action that is a FAB on a phone and a header button above, use `<x-button fab>`.
 
+     `data-fab` marks the root, so a component that nests a FAB can restyle it from its own
+     stylesheet — a rail drops its elevation to 0, as M3 asks of a nested FAB.
+
      Sizes, corners and elevation from FabBaseline/Medium/LargeTokens and ExtendedFab*Tokens
      (androidx Compose Material 3, Apache-2.0). --}}
 
@@ -63,7 +66,7 @@
         ], fn ($value): bool => $value !== null));
 @endphp
 
-<{{ $tag }} {{ $attributes }}>
+<{{ $tag }} data-fab {{ $attributes }}>
     @if ($icon)
         <x-livewire-material::icon :name="$icon" :class="$iconSize" />
     @endif