add SKILLS and AGENTS.md

[feloy]

Add:

• copyright headers skill (chore(agent): add copyright-headers skill #4 fix: make skill discoverable for several agents #5)
• conventional commits skill (feat: add commit skill for conventional commit messages #56)
• AGENTS.md and CLAUDE.md (chore(agent): add AGENTS.md and CLAUDE.md (symlink) #6)
• skills to add commands (with json output, root cmd, alias cmd, etc) (feat(skills): add command creation skills for CLI development #68)

[feloy]

done