Explain an Unfamiliar Codebase to a New Dev

Onboard me onto this codebase. I am a competent developer but I have never seen this project.

Here is the structure and key files:
"""
[PASTE FILE TREE AND/OR IMPORTANT FILES]
"""

Produce:

1. **What this project does** - 3 sentences, no marketing language.
2. **Entry points** - where execution starts, and what triggers each path.
3. **Data flow** - trace one real request or command from input to output, naming the files it passes through.
4. **The five files I must read first** - in order, with one line on why each matters.
5. **Conventions** - naming, error handling, test layout, anything a newcomer would get wrong.
6. **Sharp edges** - global state, hidden coupling, config that must be set, things that break silently.

Rules:
- Mark anything you are inferring rather than reading as "inferred".
- Do not describe files you were not shown.
- Prefer naming specific functions and line references over generalities.