Enhance Copilot instructions with agent best practices

[Copilot]

Adds guidance for effective use of GitHub Copilot coding agent based on official best practices.

Changes

• Tool Calling and Efficiency: Documents parallel vs sequential tool execution patterns to optimize agent performance
• Task Suitability Matrix: Defines which tasks are ideal for Copilot (bug fixes, tests, documentation) vs those requiring human judgment (architecture, security, domain logic)
• Agent Workflow: Guidelines for issue writing, iteration cycles, and progress monitoring

Repository already had comprehensive technical documentation. These additions focus specifically on human-AI collaboration patterns.

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 #22

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💡 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.