fix: use cross-only fullscreen diagram close control

src/components/ArchifyDiagram/index.tsx

@@ -20,7 +20,7 @@ export default function ArchifyDiagram({name, title, compact = false}: {name: st
     <div className="archify-toolbar"><button ref={opener} type="button" className="archify-expand" aria-label={`Expand ${title}`} title="Expand diagram" onClick={() => setExpanded(true)}><svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" aria-hidden="true"><path d="M8 3H3v5M16 3h5v5M21 16v5h-5M8 21H3v-5" /></svg></button></div>
     <iframe src={source} title={title} sandbox="allow-scripts allow-downloads" loading="lazy" referrerPolicy="no-referrer" />
     <dialog ref={dialog} className="archify-modal" aria-labelledby={headingId} onClose={() => {setExpanded(false); opener.current?.focus();}}>
-      <div className="archify-modal-toolbar"><strong id={headingId}>{title}</strong><button type="button" onClick={close} autoFocus aria-label="Close full-screen diagram">Close ×</button></div>
+      <div className="archify-modal-toolbar"><strong id={headingId}>{title}</strong><button type="button" onClick={close} autoFocus aria-label="Close full-screen diagram"><span aria-hidden="true">×</span></button></div>
       {expanded && <iframe src={source} title={`${title} — expanded`} sandbox="allow-scripts allow-downloads" referrerPolicy="no-referrer" />}
     </dialog>
   </section>;