Agents.md update

[A-Artemis]

Summary

Small updates to the agents.md

Checklist

• The PR title and description are clear and descriptive
• I have manually tested the changes
• All changes are covered by automated tests
• All related issues are linked to this PR (if applicable)
• Documentation has been updated (if applicable)

[github-actions]

⏱️ Backend import time — app.main

Accelerator	Cumulative (s)	Self (s)
cpu	4.621	0.003
xpu	5.380	0.003
cuda	4.521	0.003

[Copilot]

Pull request overview

Updates the repo-wide AGENTS.md guide to better document skill validation/enforcement, backend data/state directories, and a few developer workflow commands for backend/UI contributors.

Changes:

• Documented skills layout requirements (SKILL.md) and CI enforcement via the skills.yaml workflow.
• Expanded backend data/state notes to include output/ and staged_datasets/, and documented demo seeding via just run-server --setup-demo.
• Updated UI OpenAPI spec sync note and added the backend CI workflow to the “source of truth” list.