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/panels/left/PagesPanel.tsx

@@ -1,5 +1,6 @@
 import React, { useState } from 'react';
 import { usePages } from '../../state/PageContext';
+import { clickableProps } from '../../utils/a11y';
 
 export const PagesPanel: React.FC = () => {
   const {
@@ -286,7 +287,7 @@ export const PagesPanel: React.FC = () => {
           ) : (
             /* Normal page item */
             <div
-              onClick={() => switchPage(page.id)}
+              {...clickableProps(() => switchPage(page.id))}
               style={{
                 display: 'flex',
                 alignItems: 'center',