[feature] Agent Skills

Need to add skills support, details here:
- https://github.com/anthropics/skills
- https://www.anthropic.com/engineering/equipping-agents-for-the-real-world-with-agent-skills
- https://platform.claude.com/docs/en/agents-and-tools/agent-skills/overview
- https://github.com/anthropics/claude-cookbooks/tree/main/skills

Depend on #142