Add GitHub Actions workflow for Copilot environment setup with reusable .NET build action

[Copilot]

This PR adds a new GitHub Actions workflow to preconfigure the environment before GitHub Copilot agents start working on the repository. The workflow follows best practices for Copilot integration and maintains consistency with existing CI/CD workflows.

Changes Made

New Workflow File

• .github/workflows/copilot-setup-steps.yml - Main workflow that sets up .NET environment and builds the project for Copilot

Reusable Composite Action

• .github/actions/setup-dotnet-build/action.yml - New reusable composite action that handles .NET setup, dependency restoration, and building
• Updated build-and-test.yml - Now uses the reusable action to eliminate code duplication

Workflow Features

The new copilot-setup-steps job includes:

1. Environment Setup: Configures .NET (versions 3.1.x, 6.x) consistent with existing build workflows
2. Dependency Management: Restores .NET packages via dotnet restore
3. Project Building: Builds the project so Copilot has access to compiled artifacts for better code analysis
4. Security: Uses minimal permissions (contents: read only) following security best practices
5. Triggers:
   • Automatically runs on changes to the workflow file itself (push/PR events)
   • Supports manual execution via workflow_dispatch

Consistency with Existing Workflows

The implementation maintains consistency with the repository's existing CI/CD patterns:

• Uses the same shell (pwsh) and runner (ubuntu-latest)
• Follows the same .NET version strategy as build-and-test.yml
• Uses established action versions (actions/checkout@v5, actions/setup-dotnet@v4)
• Maintains the same structural patterns and naming conventions
• Introduces reusable actions to reduce duplication across workflows

This workflow ensures Copilot agents have access to a properly configured .NET development environment with compiled artifacts before beginning code analysis or generation tasks.

This pull request was created as a result of the following prompt from Copilot chat.

Create a new GitHub Actions workflow file to preconfigure Copilot's environment before the agent starts. The workflow file should be located at .github/workflows/copilot-setup-steps.yml and contain a single job named copilot-setup-steps. Follow the best practices outlined in the GitHub Copilot Agents documentation, ensuring the job uses minimal permissions required and reusable actions for consistency. Prefer modular reusable actions for repeatable tasks like setting up .NET or Node.js, as referenced in the existing build and test CI workflows, but avoid over-modularization. The workflow should use the same triggers as the example provided:

• Automatically run on changes to .github/workflows/copilot-setup-steps.yml (push and pull request events)
• Manual triggers via workflow_dispatch

The job should include the following steps:

1. Check out the code using actions/checkout@v5.
2. Set up Node.js using actions/setup-node@v4 with Node.js version 20 and npm caching.
3. Install JavaScript dependencies using npm ci.
4. Set up .NET environment, ensuring consistency with existing build and test CI workflows by using reusable actions where applicable.
5. Include any other environment-specific setup steps required for Copilot to function effectively.

---

💡 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.