Add GitHub Actions workflow for Copilot agent environment setup (#163)

## Overview
This PR adds a new GitHub Actions workflow file
`.github/workflows/copilot-setup-steps.yml` to preconfigure the
environment for GitHub Copilot agents. This workflow ensures that
Copilot agents have the necessary dependencies and tools installed
before they begin their operations.

## Changes
- Created `.github/workflows/copilot-setup-steps.yml` with a job named
`copilot-setup-steps` (required by GitHub Copilot)
- Integrated setup steps from the existing `build-and-test.yml` workflow
to ensure consistency:
  - Checkout code using `actions/checkout@v5`
- Setup .NET SDK with versions 3.1.x and 8.x using
`actions/setup-dotnet@v5`
  - Restore project dependencies with `dotnet restore`

## Workflow Configuration
- **Runs on**: `ubuntu-latest`
- **Permissions**: `contents: read` (minimal permissions required)
- **Triggers**:
  - Manual dispatch via the Actions tab
- Automatic execution on push/PR when the workflow file itself is
modified (for easy validation)

## Benefits
- GitHub Copilot agents will have a properly configured .NET environment
with all dependencies restored
- Reduces setup time and potential errors during agent operations
- Maintains consistency with the existing CI/CD pipeline setup steps
- Allows for easy testing and validation of the setup process

This workflow follows GitHub's recommended pattern for Copilot agent
setup and uses the same action versions as the existing
`build-and-test.yml` workflow for consistency.

<!-- START COPILOT CODING AGENT SUFFIX -->



<details>

<summary>Original prompt</summary>

> Create a GitHub Actions workflow file at
.github/workflows/copilot-setup-steps.yml to preconfigure the
environment for GitHub Copilot agents. The workflow should include a
single job named 'copilot-setup-steps'. Integrate setup and reusable
actions from the existing build and test CI workflows to ensure
consistency and proper environment configuration.
> 
> ex:
> 
> ```
> 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
> etc...
> ```


</details>


<!-- START COPILOT CODING AGENT TIPS -->
---

✨ Let Copilot coding agent [set things up for
you](https://github.com/IntelliTect/Multitool/issues/new?title=✨+Set+up+Copilot+instructions&body=Configure%20instructions%20for%20this%20repository%20as%20documented%20in%20%5BBest%20practices%20for%20Copilot%20coding%20agent%20in%20your%20repository%5D%28https://gh.io/copilot-coding-agent-tips%29%2E%0A%0A%3COnboard%20this%20repo%3E&assignees=copilot)
— coding agent works faster and does higher quality work when set up for
your repo.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: BenjaminMichaelis <22186029+BenjaminMichaelis@users.noreply.github.com>
Co-authored-by: Benjamin Michaelis <git@relay.benjamin.michaelis.net>

Author: Copilot

.github/workflows/build-and-test.yml

@@ -23,9 +23,7 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v5
       with:
-        dotnet-version: | 
-            3.1.x
-            8.x
+        global-json-file: global.json
     - name: Restore dependencies
       run: dotnet restore
     - name: Build

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

@@ -0,0 +1,37 @@
+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: Setup .NET
+        uses: actions/setup-dotnet@v5
+        with:
+          global-json-file: global.json
+      
+      - name: Restore dependencies
+        run: dotnet restore