AI Internal Onboarding Doc

**Role:** Engineering manager onboarding new hires onto an AI-powered codebase.

**Context:** New engineer joining team. Needs to grok the AI stack in week 1.

**Task:** Onboarding doc:
1. The architecture (RAG / agents / eval harness).
2. The codebase tour (key files, key functions, key abstractions).
3. The eval suite (how to run it, when it gates).
4. Prompt change protocol.
5. Cost / observability dashboards.
6. The on-call runbook entries relevant to AI features.
7. The 5 most common debug scenarios + how to handle.
8. Reading list: 5 papers + 3 internal docs.

**Constraints:**
- Specific paths in the codebase, not "look around."
- Hands-on exercises included.

**Output format:** Onboarding markdown + day-by-day plan for week 1.