Refactor documentation and templates for AI coding agents

[marko-stanojevic]

This pull request makes several documentation and workflow improvements to the repository, focusing on refining guidance for AI coding agents, updating templates, and improving clarity for security and workflow operations. The most significant changes are a complete rewrite of AGENTS.md to provide more actionable and strict guidelines for AI-generated code, removal of redundant copilot instructions, and updates to security and workflow templates.

AI Agent and Contributor Guidance:

• Rewrote AGENTS.md to provide comprehensive, actionable guidelines for AI coding agents, including hard rules, coding patterns, error handling, parameter validation, testing requirements, CI/CD expectations, and an AI-friendly function template. The new document emphasizes production-readiness, maintainability, and auditability.
• Removed .github/copilot-instructions.mdt to consolidate and avoid duplication of AI agent guidance, with all relevant information now in AGENTS.md.

Workflow and Template Updates:

• Added a run-name to .github/workflows/bootstrap-repo.yml for clearer workflow identification in GitHub Actions runs.
• Updated .github/PULL_REQUEST_TEMPLATE.md to suggest using GitHub Copilot for generating PR descriptions, improving contributor experience.

Security Documentation:

• Revised .github/SECURITY.md instructions to clarify the process for reporting vulnerabilities, updating navigation to use "Advisories" and "New draft security advisory".