Stephan Behnke 98859f32f8 Review agent guidelines (#8973) ...

## What changed?

Added prompt ("skill") for AI review agents.

Note that the source of truth file is in `.github` since it's the only
agent that does not support file references.

## Why?

There are common review issues that cannot be linted easily that we want
to enforce without human intervention.

## How did you test it?

Added a violation and ran review agents:

### Cursor 

<img width="819" height="339" alt="image"
src="https://github.com/user-attachments/assets/655aee7f-1b0c-4e7f-8ef5-60ea543d21cd"
/>

### Copilot

<img width="827" height="354" alt="image"
src="https://github.com/user-attachments/assets/cac3a819-d115-49ff-9b0c-1a51db162720"
/>

### Claude Code via `/review`

<img width="578" height="352" alt="Screenshot 2026-01-08 at 11 21 15 AM"
src="https://github.com/user-attachments/assets/057b911d-c4e4-4eda-8a99-c66480de7bb3"
/>

2026-02-18 02:16:42 +00:00

..

review

Review agent guidelines (#8973)

2026-02-18 02:16:42 +00:00