onboarding-guidelisted

# Onboarding guide Use when writing onboarding docs — get a newcomer to a working change on day one. ## Checklist - Start with the shortest path to a running app and a passing test suite. - Explain the mental model before the directory tree. - List the accounts, keys, and access needed, and who grants them. - Name the three things that trip up every new person. - End with a small starter task that touches the real codebase. - Have the next newcomer fix the guide as their first PR.