feat(cli): add direct model inference via new run subcommand
- Add `aha run` CLI subcommand for direct model inference without HTTP service
- Support multiple models including Qwen series, OCR models, ASR models, and voice generation
- Implement input/output handling with file path support and auto-generation
- Add comprehensive documentation in CLI_USAGE.md with examples
- Include performance timing for model loading and inference operations
- Add macOS build target to Makefile with Metal support
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- **CLI Subcommand Support**: Added three new subcommands for better command organization:
- `aha cli` - Download model and start HTTP service (default, backward compatible)
- `aha serv` - Start HTTP service only (requires `--weight-path`)
- `aha download` - Download model only (no service start)
XiaoYang