docs: add comprehensive QWEN.md project context file

Add detailed project documentation for AI agents and developers:
- Project overview and architecture diagram
- Complete directory structure with descriptions
- Building and running instructions
- Development conventions (SDD workflow, code style, pre-commit)
- CI/CD pipeline descriptions
- API reference with function signatures
- Performance targets and current status
- Common development task guides
- Troubleshooting section

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

Author: shijiashuai