fix: add missing aria-labels to icon-only buttons for accessibility

- ChatInput: add aria-labels to remove file, send shortcut toggle, and stop buttons
- CodeBlock: add aria-labels to word wrap, line numbers, and collapse/expand buttons
- Header: add aria-labels to session info, copy, close, and compact buttons

src/components/ChatInput.tsx

@@ -296,6 +296,7 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled, sessionKey,
                   <button
                     onClick={() => removeFile(f.id)}
                     className="absolute -top-1.5 -right-1.5 h-5 w-5 rounded-full bg-pc-elevated border border-pc-border-strong flex items-center justify-center opacity-0 group-hover:opacity-100 transition-opacity hover:bg-red-500/80"
+                    aria-label={`Remove ${f.file.name}`}
                   >
                     <X size={10} className="text-pc-text" />
                   </button>
@@ -360,6 +361,7 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled, sessionKey,
               onClick={toggleSendShortcut}
               className="hidden sm:flex shrink-0 h-7 rounded-xl border border-pc-border bg-pc-elevated/30 px-2 items-center gap-1 text-[10px] text-pc-text-muted hover:text-pc-text-secondary hover:bg-[var(--pc-hover)] transition-colors"
               title={`${t('settings.sendShortcut')}: ${sendOnEnter ? t('settings.sendEnter') : t('settings.sendCtrlEnter')}`}
+              aria-label={`${t('settings.sendShortcut')}: ${sendOnEnter ? t('settings.sendEnter') : t('settings.sendCtrlEnter')}`}
             >
               <span>{sendOnEnter ? '↵' : (navigator.userAgent.includes('Mac') ? '⌘↵' : 'Ctrl↵')}</span>
             </button>
@@ -367,6 +369,7 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled, sessionKey,
               <button
                 onClick={onAbort}
                 className="shrink-0 h-11 px-4 rounded-2xl border border-red-500/20 bg-red-500/10 text-red-400 hover:bg-red-500/20 transition-colors flex items-center gap-2"
+                aria-label={t('chat.stop')}
               >
                 <Square size={16} />
                 <span className="text-sm hidden sm:inline">{t('chat.stop')}</span>

src/components/CodeBlock.tsx

@@ -111,6 +111,7 @@ export function CodeBlock(props: HTMLAttributes<HTMLPreElement>) {
               onClick={toggleWrap}
               className="flex items-center gap-1 px-1.5 py-0.5 rounded hover:bg-pc-border/40 transition-colors text-pc-text-muted hover:text-pc-text-secondary"
               title={wordWrap ? 'Disable word wrap' : 'Enable word wrap'}
+              aria-label={wordWrap ? 'Disable word wrap' : 'Enable word wrap'}
               type="button"
             >
               {wordWrap ? <AlignLeft className="h-3 w-3" /> : <WrapText className="h-3 w-3" />}
@@ -120,6 +121,7 @@ export function CodeBlock(props: HTMLAttributes<HTMLPreElement>) {
                 onClick={toggleLineNumbers}
                 className="flex items-center gap-1 px-1.5 py-0.5 rounded hover:bg-pc-border/40 transition-colors text-pc-text-muted hover:text-pc-text-secondary"
                 title={showLineNumbers ? 'Hide line numbers' : 'Show line numbers'}
+                aria-label={showLineNumbers ? 'Hide line numbers' : 'Show line numbers'}
                 type="button"
               >
                 <Hash className="h-3 w-3" />
@@ -155,6 +157,7 @@ export function CodeBlock(props: HTMLAttributes<HTMLPreElement>) {
         <button
           onClick={() => setIsCollapsed(prev => !prev)}
           className="flex items-center justify-center gap-1.5 w-full py-1.5 text-[11px] text-pc-text-muted hover:text-pc-text-secondary bg-pc-elevated/40 hover:bg-pc-elevated/60 border-t border-pc-border transition-colors rounded-b-lg"
+          aria-label={isCollapsed ? `Show all ${lines.length} lines` : 'Collapse code'}
           type="button"
         >
           {isCollapsed ? (

src/components/Header.tsx

@@ -62,7 +62,7 @@ export function Header({ status, sessionKey, onToggleSidebar, activeSessionData,
       </button>
       <div className="flex items-center gap-3 flex-1 min-w-0 relative" ref={sessionInfoRef}>
         <img src={agentAvatarUrl || '/logo.png'} alt="PinchChat" className="h-9 w-9 rounded-2xl object-cover" onError={(e) => { const img = e.target as HTMLImageElement; if (img.src !== window.location.origin + '/logo.png') { img.src = '/logo.png'; } else { img.style.display = 'none'; } }} />
-        <button className="min-w-0 text-left group" onClick={() => setShowSessionInfo(v => !v)} title={t('header.sessionInfo')}>
+        <button className="min-w-0 text-left group" onClick={() => setShowSessionInfo(v => !v)} title={t('header.sessionInfo')} aria-label={t('header.sessionInfo')}>
           <div className="flex items-center gap-2">
             <span className="font-semibold text-pc-text text-sm tracking-wide">{agentName || t('header.title')}</span>
             <Sparkles className="h-3.5 w-3.5 text-pc-accent-light/60" />
@@ -169,6 +169,7 @@ function CopyField({ value }: { value: string }) {
       className="ml-auto p-0.5 rounded hover:bg-[var(--pc-hover)] text-pc-text-faint hover:text-pc-text-secondary transition-colors"
       onClick={() => { copyToClipboard(value).then((ok) => { if (ok) { setCopied(true); setTimeout(() => setCopied(false), 1500); } }); }}
       title="Copy"
+      aria-label="Copy to clipboard"
     >
       {copied ? <Check size={11} className="text-emerald-400" /> : <Copy size={11} />}
     </button>
@@ -206,7 +207,7 @@ const SessionInfoPopover = forwardRef<HTMLDivElement, { session: Session; sessio
     >
       <div className="p-3 border-b border-pc-border flex items-center justify-between">
         <span className="text-xs font-semibold text-pc-text">{t('header.sessionInfo')}</span>
-        <button onClick={onClose} className="text-pc-text-faint hover:text-pc-text text-xs">✕</button>
+        <button onClick={onClose} className="text-pc-text-faint hover:text-pc-text text-xs" aria-label="Close">✕</button>
       </div>
       <div className="p-3 space-y-2">
         {rows.map(({ label, value, copyable }) => (
@@ -241,6 +242,7 @@ function CompactButton({ sessionKey, onCompact }: { sessionKey: string; onCompac
       disabled={compacting}
       className="inline-flex items-center gap-1 text-[10px] text-pc-text-muted hover:text-pc-text shrink-0 px-1.5 py-0.5 rounded hover:bg-[var(--pc-hover)] transition-colors disabled:opacity-50"
       title={t('header.compact')}
+      aria-label={t('header.compact')}
     >
       <Minimize2 className={`h-3 w-3 ${compacting ? 'animate-pulse' : ''}`} />
       <span className="hidden sm:inline">{compacting ? t('header.compacting') : t('header.compact')}</span>