fix(a11y): accessible names for icon links and the copy button

- aria-labels on share links, sidebar social links and mobile nav icons
- aria-current on active nav links
- CopyButton: React state instead of innerHTML mutation, clipboard error
  handling, accessible label and a polite live region for feedback

(Related code-block and image-caption a11y fixes landed with the
ImageWrapper/CodeWrapper rewrite in the previous perf commit.)

components/layout/MobileNavbar.tsx

@@ -24,6 +24,8 @@ export function MobileNavbar() {
             <Link
               key={item.href}
               href={item.href}
+              aria-label={item.label}
+              aria-current={isActive(item.href) ? 'page' : undefined}
               className={cn(
                 'transition-colors',
                 isActive(item.href) ? 'text-accent' : 'text-fg-dim hover:text-fg',

components/layout/NavLinks.tsx

@@ -34,7 +34,11 @@ export function NavLinks() {
           {item.label}
         </ExternalLink>
       ) : (
-        <Link href={item.href} className="flex items-center gap-2 px-2 py-1">
+        <Link
+          href={item.href}
+          className="flex items-center gap-2 px-2 py-1"
+          aria-current={isActive(item.href) ? 'page' : undefined}
+        >
           {item.icon}
           {item.label}
         </Link>

components/layout/Sidebar.tsx

@@ -47,8 +47,9 @@ export async function Sidebar() {
         </div>
         <div className="mt-auto flex gap-4 mx-auto">
           {socialLinks.map(({ icon, url }) => (
-            <ExternalLink key={url} href={url} skipIcon>
+            <ExternalLink key={url} href={url} skipIcon aria-label={icon.title}>
               <svg
+                aria-hidden="true"
                 dangerouslySetInnerHTML={{ __html: icon.svg }}
                 className="inline-block w-6 h-6 mr-1 fill-fg-dim hover:fill-accent transition-colors"
               />

components/post/ShareLinks.tsx

@@ -38,8 +38,9 @@ export function ShareLinks({ url, title, description }: ShareLinksProps) {
   return (
     <div className="flex gap-4 mx-auto">
       {networks.map(({ name, icon, href }) => (
-        <ExternalLink key={name} href={href} skipIcon>
+        <ExternalLink key={name} href={href} skipIcon aria-label={`Share on ${name}`}>
           <svg
+            aria-hidden="true"
             dangerouslySetInnerHTML={{ __html: icon.svg }}
             className="inline-block w-6 h-6 mr-1 fill-current hover:text-accent transition-colors"
           />

components/ui/CopyButton.tsx

@@ -1,41 +1,66 @@
 'use client'
 
-import { ButtonHTMLAttributes, useRef } from 'react'
-import { Copy } from 'lucide-react'
+import { ButtonHTMLAttributes, useEffect, useState } from 'react'
+import { Check, Copy } from 'lucide-react'
 import { cn } from '@/utils/cn'
 
 type CopyButtonProps = ButtonHTMLAttributes<HTMLButtonElement> & {
   textToCopy: string
 }
 
-export function CopyButton({ textToCopy, className, ...props }: CopyButtonProps) {
-  const buttonRef = useRef<HTMLButtonElement | null>(null)
+type CopyState = 'idle' | 'copied' | 'failed'
 
-  const handleCopy = () => {
-    navigator.clipboard.writeText(textToCopy)
-    const button = buttonRef.current
-    if (button) {
-      const original = button.innerHTML
-      button.innerHTML = 'Copied!'
-      button.disabled = true
-      setTimeout(() => {
-        button.innerHTML = original
-        button.disabled = false
-      }, 2000)
+const labels: Record<CopyState, string> = {
+  idle: 'Copy code',
+  copied: 'Copied!',
+  failed: 'Copy failed',
+}
+
+export function CopyButton({ textToCopy, className, ...props }: CopyButtonProps) {
+  const [state, setState] = useState<CopyState>('idle')
+
+  useEffect(() => {
+    if (state === 'idle') return
+    const timeout = setTimeout(() => setState('idle'), 2000)
+    return () => clearTimeout(timeout)
+  }, [state])
+
+  const handleCopy = async () => {
+    try {
+      await navigator.clipboard.writeText(textToCopy)
+      setState('copied')
+    } catch {
+      setState('failed')
     }
   }
 
   return (
-    <button
-      className={cn(
-        'text-fg-dim hover:text-fg transition-colors js-only text-xs cursor-pointer disabled:cursor-default disabled:hover:text-fg-dim',
-        className,
-      )}
-      onClick={handleCopy}
-      ref={buttonRef}
-      {...props}
-    >
-      <Copy className="w-4 h-4" />
-    </button>
+    <>
+      <button
+        type="button"
+        className={cn(
+          'text-fg-dim hover:text-fg transition-colors js-only text-xs cursor-pointer disabled:cursor-default disabled:hover:text-fg-dim',
+          className,
+        )}
+        onClick={handleCopy}
+        disabled={state !== 'idle'}
+        aria-label={labels.idle}
+        title={labels.idle}
+        {...props}
+      >
+        {state === 'idle' ? (
+          <Copy className="w-4 h-4" />
+        ) : (
+          <span className="flex items-center gap-1">
+            {state === 'copied' && <Check className="w-4 h-4" />}
+            {labels[state]}
+          </span>
+        )}
+      </button>
+      {/* Outside the button: a button's children are presentational, so they aren't announced */}
+      <span className="sr-only" aria-live="polite">
+        {state === 'idle' ? '' : labels[state]}
+      </span>
+    </>
   )
 }