Add comprehensive GitHub Copilot instructions for CNDP development workflow

[Copilot]

This PR adds a comprehensive .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed instructions for working effectively in the CNDP codebase.

What's Included

The instructions provide exhaustively validated commands and workflows covering:

Development Setup:

• Complete dependency installation (libbpf, meson, system packages)
• Environment configuration with proper PATH and PKG_CONFIG_PATH setup
• Build system usage (Meson + Makefile wrapper via tools/cne-build.sh)

Build & Test Workflows:

• Exact build commands with measured timing expectations
• Test suite execution (meson test -C builddir --suite short)
• Example application validation (helloworld, cndpfwd, cli)

Critical Timeout Information:

• Build operations: ~40-45 seconds (recommended 120s timeout)
• Test suite: ~4-5 seconds (recommended 30s timeout)
• NEVER CANCEL warnings for all long-running operations

Code Quality:

• Formatting via ninja -C builddir clang-format
• Repository structure explanation with key directories
• Common troubleshooting scenarios

Validation Process

Every single command in the instructions has been exhaustively tested from a fresh environment:

• ✅ Complete dependency installation and build from scratch
• ✅ All 25/26 tests pass (1 expected skip)
• ✅ Example applications run correctly
• ✅ Clean/rebuild cycles work as documented
• ✅ Code formatting tools function properly

The instructions follow the imperative tone requirement ("Run this command", "Do not do this") and include explicit guidance to reference these instructions first before falling back to additional context gathering.

This enables GitHub Copilot agents to work efficiently in the CNDP codebase without trial-and-error, reducing development friction for contributors working with this high-performance packet processing framework.

Fixes #440.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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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.