feat: add user requirements analysis feature

[wwch123]

feat: add user requirements analysis feature in chat mode

🎯 Overview

Adds intelligent requirement gathering to chat interface - AI generates targeted questions to help users provide more detailed project requirements before code generation.

✨ Key Features

• Guided Analysis Mode: AI asks 5-8 smart questions based on user's initial input
• Flexible Interaction: Users can answer, skip, or provide partial responses
• Smart Question Generation: Context-aware questions for web apps, data analysis, ML projects
• Structured Output: AI synthesizes answers into comprehensive requirement documents

🔧 Implementation

• New RequirementAnalysisAgent following MCP Agent architecture
• Enhanced UI with 3-step workflow: Input → Questions → Requirements Review
• Async processing with progress tracking
• Robust error handling with intelligent fallbacks

🚀 User Flow

1. Select "Guided Analysis" in chat
2. Enter basic project idea
3. Answer AI-generated questions
4. Review detailed requirements
5. Proceed to code generation

💡 Benefits

• Better Code Quality: More detailed requirements → more accurate implementations
• User Guidance: Helps users consider aspects they might miss
• Reduced Iterations: Fewer clarification rounds needed
• Backward Compatible: Existing direct input unchanged