Add GitHub Actions workflow documenting MeshKernel build environment setup

[Copilot]

Created .github/workflows/copilot-setup-steps.yml to document the complete build environment setup for MeshKernel, serving as executable documentation for developers and Copilot.

Detected Stack

• C++20 with CMake 3.23+ build system
• Python 3.x for utility scripts (benchmark processing, CI automation)
• PowerShell for cross-platform dependency installation

Setup Actions Configured

• Compiler: GCC 12 (C++20 support required)
• Build system: CMake via jwlawson/actions-setup-cmake@v2
• System dependencies: Boost (libboost-all-dev), Doxygen
• Language runtimes: Python via actions/setup-python@v5, PowerShell
• External dependencies: NetCDF built from source using repository's install_netcdf_static.ps1

Permissions

Set to minimal contents: read only.

Workflow Structure

16 documented steps from checkout through build/test, each with inline explanations of purpose and technical requirements. Manually triggered via workflow_dispatch for reference and validation purposes.

Original prompt

“Generate .github/workflows/copilot-setup-steps.yml for this repository. Detect language(s), choose the right setup actions, and preinstall all dependencies. Add minimal permissions and explain each step.”

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