chore: add quick-start header to SKILL.md

[dennisonbertram]

SKILL.md is 350 lines. The actual "I have an API key, what do I do?" content is buried after a full server bootstrap guide.

Add a 5–10 line Quick Start block at the very top (after frontmatter) so Claude can orient immediately:

## Quick Start
export AH_URL="https://<your-server>"
export AH_KEY="<keyid.secret>"

/status    → see what's running
/deploy    → deploy a service
/logs      → stream build logs
/db        → provision postgres or redis

Everything else stays as-is — the detailed reference and server setup guide remain for when they're needed.