Add comprehensive Copilot instructions for coding agent

[Copilot]

✅ Copilot Instructions Enhancement Complete

Successfully enhanced .github/copilot-instructions.md with comprehensive guidelines for the GitHub Copilot coding agent following official best practices.

Checklist:

• Review existing copilot-instructions.md file
• Analyze repository structure and conventions from existing files
• Add code style and formatting conventions section
• Add testing practices and patterns section
• Add dependency management guidelines
• Add API key and secrets management information
• Add common workflows and troubleshooting section
• Add protobuf and code generation specifics
• Validate enhanced instructions with code review
• Run security scanning (CodeQL)
• Address feedback - remove lock files reference
• Final review and commit

Summary

Enhanced the Copilot instructions with 146 lines of comprehensive documentation covering:

✅ Code Style & Formatting - EditorConfig rules, formatting validation
✅ Testing Practices - xUnit framework, custom attributes, API key management
✅ Dependency Management - Package sources, key dependencies
✅ Protobuf & Code Generation - Auto-sync process, generation warnings
✅ Troubleshooting - Common build/test issues and solutions
✅ Multi-Targeting - Framework specifications and considerations
✅ Special Tools - dnx command, MSBuild configuration
✅ Microsoft.Extensions.AI - Integration patterns and tool support
✅ Security - API key handling, code quality standards

Validation

• ✅ Code review passed with no issues
• ✅ CodeQL security scan passed (no code changes to analyze)
• ✅ Documentation-only change (no build impact)
• ✅ Feedback addressed - corrected lock files reference

The enhanced instructions follow GitHub's official best practices and will help Copilot coding agent work more effectively with this repository.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>✨ Set up Copilot instructions</issue_title>
<issue_description>Configure instructions for this repository as documented in Best practices for Copilot coding agent in your repository.

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes ✨ Set up Copilot instructions #46

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[kzu]

@copilot .github/copilot-instructions.md:121 I don't use lock files

[Copilot]

@copilot .github/copilot-instructions.md:121 I don't use lock files

Fixed in 5820111 - changed "update lock files" to "update dependencies".

[kzu]

🧪 Details on Ubuntu 24.04.3 LTS

from retest v1.1.0 on .NET 10.0.1 with 💜 by @devlooped