core-codebase-onboardinglisted

# Codebase Onboarding A structured orientation beats wandering. Every minute spent mapping the codebase pays back ten minutes in informed editing. Without a map, agents wander depth-first, accumulate false assumptions, and make changes that ripple through layers they never read. This skill gives you the map before the territory. --- ## What This Skill Is (and isn't) **Is:** Doctrine for the orientation agent spawned by `/onboard <path>`. It prescribes a phase-ordered workflow that produces a finite, actionable orientation report. The agent follows the phases in order, applies the hard rules throughout, and delivers the output contract at the end. **Is not:** - A debugging skill (see `core/observability-and-ops`) - A code-review skill (see `core/code-review-checklist`) - A refactoring plan — orientation produces a MAP, not a change list - A substitute for reading the actual code — the report is a navigation aid, not a summary that absolves the agent from reading files it will edit **Paired with:** `/onboard` slash command (`.claude/commands/onboard.md`), which is the user-facing trigger. The slash command spawns this agent; this skill loads the doctrine. --- ## Phase Sequence Execute phases **in order**. Do not skip phases. Do not start Phase N+1 while Phase N is incomplete. Each phase has a goal and produces a named output that feeds the next phase. ### Phase 0 — Governance context (goal: know the project's own rules) Before reading any source code, read the pro