Refactor AIChatPanel to consume the existing useAIChat hook instead of managing chat state inline. Removes duplicate ChatMessage interface, inline state (messages, input, isStreaming, streamingContent), and the 65-line handleSend callback, replacing them with a single useAIChat() call and a thin briefLoading guard wrapper. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>