feat(skills): add built-in skill packaging mechanism and about-picobot documentation
- Add build.rs: scan resources/skills/, compress each with tar+zstd, embed via include_bytes!
- Add src/skills/builtin.rs: runtime auto-install built-in skills to ~/.picobot/skills/
- Add about-picobot built-in skill: SKILL.md index + references/ (config, db-schema, architecture, faq, commands) + assets/config.example.json
- Update skill loading: reverse priority (agents < picobot < workspace), deduplicate by name
- Update skills prompt: re-query get_skill when user asks about installed skills
- Change max_tool_iterations default from 20 to 99
xiaoski
2f11aed44a