a11y: keyboard-operable editor chrome + topbar aria-labels

Clickable <div> rows/tiles (page list, layer tree, template cards, asset
picker grid) now expose role="button", a tab stop, and Enter/Space
activation via a shared clickableProps() helper, matching their existing
onClick behavior. TopBar icon-only controls (device switcher, undo/redo,
save, publish, templates, code, preview, back) gain aria-label alongside
their existing title tooltips.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/ui/AssetPicker.tsx

@@ -1,5 +1,6 @@
 import React, { useState, useCallback, useRef, useEffect, CSSProperties } from 'react';
 import { uploadAsset, listAssets, Asset } from '../utils/assets';
+import { clickableProps } from '../utils/a11y';
 
 export interface AssetPickerProps {
   value: string;
@@ -192,7 +193,7 @@ export const AssetPicker: React.FC<AssetPickerProps> = ({
       {browserAssets.map((asset) => (
         <div
           key={asset.name}
-          onClick={() => handleSelectAsset(asset)}
+          {...clickableProps(() => handleSelectAsset(asset))}
           data-testid={`asset-picker-thumb-${asset.name}`}
           style={{ cursor: 'pointer', borderRadius: 4, overflow: 'hidden', border: '2px solid transparent', aspectRatio: '1' }}
         >