Align AGENTS.md with canonical sections, retire HUB references, fix SECURITY.md links

[glenn-jocher]

Standardizes this repo against the Ultralytics org conventions and fixes inaccuracies in the org-wide default community-health files that every Ultralytics repo without its own copy inherits.

• AGENTS.md: replaced the repo-local Core Principles rewrite with the canonical 5-principle version. The old text carried an Output gate requiring every PR body to contain a Deleted: line, which contradicts the canonical review gate ("a missing or thin PR description is never itself a finding"). Also replaced the drifted 4-step PR Workflow with the canonical 5-step version and added the missing repo-specific intro. Commands, Architecture, and Conventions are preserved; the dropped org-wide-defaults warning is already stated verbatim in Architecture.
• SECURITY.md: the Snyk Advisor badge image 404s (snyk.io/advisor/python/ultralytics/badge.svg), so it renders broken in every repo that inherits this file. Swapped in the shields.io badge already used by ultralytics/ultralytics docs.
• SECURITY.md: the Summary closed with "visit our export documentation" — a docs-site relative path that resolves to github.com/ultralytics/modes/export.md on GitHub, and unrelated to security tooling. Restored the canonical sentence.
• Ultralytics HUB shut down on July 31, 2026 and was replaced by Ultralytics Platform. Retired four references that still present it as a current product: README.md, CODE_OF_CONDUCT.md, and the repository placeholders in ISSUE_TEMPLATE/feature-request.yml and ISSUE_TEMPLATE/question.yml.
• ISSUE_TEMPLATE/bug-report.yml: the placeholder cited a "YOLOv8 PyPI package", which does not exist — the package is ultralytics.

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated organization-wide community and security documentation to reflect the Ultralytics Platform branding and clarified AI-agent development guidance. ✨

📊 Key Changes

• Replaced outdated Ultralytics HUB references with Ultralytics Platform across issue templates, the code of conduct, and the README.
• Updated the bug-report example from "YOLOv8 PyPI package" to "ultralytics PyPI package".
• Reworked AGENTS.md to:
  • Clarify the purpose and organization-wide impact of the .github repository.
  • Simplify development principles around deleting, reusing, and modifying existing code.
  • Refine review, validation, PR, and worktree workflows.
• Updated the Snyk security badge to use a Shields.io badge linking directly to Snyk security information.
• Replaced an outdated relative security-documentation link with guidance to review the security sections or contact the security team.

🎯 Purpose & Impact

• 🧭 Provides consistent, current product naming across Ultralytics repositories and community workflows.
• 🤖 Gives AI coding agents clearer instructions for making minimal, maintainable, and production-ready changes.
• 🔐 Improves the reliability and presentation of security documentation and scanning references.
• 🌍 Because .github files are inherited by repositories across the organization, these updates improve consistency for contributors and users throughout Ultralytics.

[UltralyticsAssistant]

👋 Hello @glenn-jocher, thank you for submitting a ultralytics/.github 🚀 PR! This is an automated welcome message, and an engineer will assist with the review. To ensure a seamless integration of your work, please review the following checklist:

• ✅ Define a Purpose: Clearly explain the purpose of your fix or feature in your PR description, and link to any relevant issues. Ensure your commit messages are clear, concise, and adhere to the project's conventions.
• ✅ Synchronize with Source: Confirm your PR is synchronized with the ultralytics/.github main branch. If it's behind, update it by clicking the 'Update branch' button or by running git pull and git merge main locally.
• ✅ Ensure CI Checks Pass: Verify all Ultralytics Continuous Integration (CI) checks are passing. If any checks fail, please address the issues.
• ✅ Update Documentation: Update the relevant documentation for any new or modified features.
• ✅ Add Tests: If applicable, include or update tests to cover your changes, and confirm that all tests are passing.
• ✅ Sign the CLA: Please ensure you have signed our Contributor License Agreement if this is your first Ultralytics PR by writing "I have read the CLA Document and I sign the CLA" in a new message.
• ✅ Minimize Changes: Limit your changes to the minimum necessary for your bug fix or feature addition. "It is not daily increase but daily decrease, hack away the unessential. The closer to the source, the less wastage there is." — Bruce Lee

For more guidance, please refer to our Contributing Guide. Don't hesitate to leave a comment if you have any questions. Thank you for contributing to Ultralytics! 🚀

[UltralyticsAssistant]

🔍 PR Review

_{Made with ❤️ by Ultralytics Actions}

Clean PR. The replacements align the inherited templates and documentation with the repository guidance, and the SECURITY.md change removes the obsolete relative documentation link without introducing a broken repository-local reference.

[UltralyticsAssistant]

🎉 Thank you, @glenn-jocher, for this impactful contribution—and congratulations on the merge!

“Great things are done by a series of small things brought together.” — Vincent van Gogh

These thoughtful updates bring consistent Ultralytics Platform branding, clearer AI-agent guidance, and stronger security documentation across the organization. By improving the shared .github repository, you’re helping contributors and users across every Ultralytics project work with greater clarity and confidence. We truly appreciate your care and attention to detail! 🚀