feat: interactive AskUserQuestion + WebSocket stability

- Add WebSocket heartbeat (30s ping/pong) to prevent proxy timeouts
- Add auto-reconnect with exponential backoff (1s-30s, max 10 attempts)
- Add interactive AskUserQuestion rendering with clickable options
- Add custom input field for free-text answers
- Add smooth animations (hover, selection glow, checkbox scale)
- Make interactive tool cards wider (max-w-2xl) without scrolling
- Hide error badge and result section for interactive tools
- Use TextareaAutosize for lag-free custom input
- Add Skill, SlashCommand tool renderings
- Add ThinkingBlock component for collapsible <thinking> tags

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/components/ChatPanel.jsx

@@ -182,6 +182,7 @@ export const ChatPanel = memo(function ChatPanel({ sessionId }) {
         <MessageList
           messages={session.messages || []}
           isProcessing={session.isProcessing}
+          onSendMessage={handleSendMessage}
         />
       ) : (
         <WelcomeScreen session={session} onStart={start} />