Add Copilot coding agent environment setup workflow

[Copilot]

Configures the GitHub Copilot coding agent development environment to enable AI-assisted coding in this repository.

Changes

• Created .github/workflows/copilot-setup-steps.yml

  • Job named copilot-setup-steps (required by Copilot)
  • Minimal permissions: contents: read
  • Triggers on workflow_dispatch, push/PR to the workflow file itself

• Reused existing CI components

  • actions/checkout@v4 from dotnetBuild.yml
  • actions/setup-dotnet@v4 with global-json-file: "./global.json" from dotnetBuild.yml
  • dotnet restore command from dotnetBuild.yml

The workflow prepares a .NET 8.0 environment with restored dependencies before Copilot begins work, following the official GitHub documentation pattern.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Customizing the development environment for GitHub Copilot coding agent</issue_title>
<issue_description>https://docs.github.com/en/enterprise-cloud@latest/copilot/how-tos/use-copilot-agents/coding-agent/customize-the-agent-environment

Sample:

name: "Copilot Setup Steps"

# Automatically run the setup steps when they are changed to allow for easy validation, and
# allow manual testing through the repository's "Actions" tab
on:
  workflow_dispatch:
  push:
    paths:
      - .github/workflows/copilot-setup-steps.yml
  pull_request:
    paths:
      - .github/workflows/copilot-setup-steps.yml

jobs:
  # The job MUST be called `copilot-setup-steps` or it will not be picked up by Copilot.
  copilot-setup-steps:
    runs-on: ubuntu-latest

    # Set the permissions to the lowest permissions possible needed for your steps.
    # Copilot will be given its own token for its operations.
    permissions:
      # If you want to clone the repository as part of your setup steps, for example to install dependencies, you'll need the `contents: read` permission. If you don't clone the repository in your setup steps, Copilot will do this for you automatically after the steps complete.
      contents: read

    # You can define any steps you want, and they will run before the agent starts.
    # If you do not check out your code, Copilot will do this for you.
    steps:
      - name: Checkout code
        uses: actions/checkout@v5

      - name: Set up Node.js
        uses: actions/setup-node@v4
        with:
          node-version: "20"
          cache: "npm"

      - name: Install JavaScript dependencies
        run: npm ci

Reuse/share components from our existing CI pipelines where we can</issue_description>

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

• Fixes Customizing the development environment for GitHub Copilot coding agent #372

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.