Why this is a good first issue

tiny cleanup that improves consistency with the repo root AGENTS.md.

Evidence

the tests directory uses AGENTS.MD while the repo root uses AGENTS.md.

Likely files

• tests/AGENTS.MD
• any references to that file if they exist

Acceptance criteria

• rename the file to tests/AGENTS.md
• update any references if needed
• keep the file content unchanged unless required for the rename

First-time contributors

This issue is intentionally scoped to be approachable for first-time contributors: one focused change, clear files, and low regression risk.