Add GitHub Copilot instructions

[Copilot]

Configures repository-wide Copilot coding agent instructions per issue requirements.

Changes

Created .github/copilot-instructions.md covering:

• Tech stack: C# 10.0, multi-targeting (netstandard2.0/2.1, net8.0/9.0/10.0), SharpCompress/DiscUtils dependencies
• Build/test commands: dotnet build, dotnet test, dotnet restore with specific project paths
• NuGet configuration: Critical guidance for agents to temporarily switch from private Azure DevOps feed to public nuget.org when needed, with explicit requirement to restore original nuget.config before completion
• Code style: .editorconfig conventions (4-space indent, CRLF, PascalCase types/methods, camelCase parameters)
• Testing practices: xUnit patterns, test organization mirroring source structure
• Security: ZipSlip/Quine/Zip Bomb protections, resource cleanup requirements
• Common patterns: Extraction API patterns, custom extractor implementation (ICustomAsyncExtractor), error handling

NuGet Feed Example

<!-- Temporary public feed configuration for agents -->
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <clear />
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
  </packageSources>
</configuration>

Agents must revert to original private feed configuration before completing work.

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:

• gh.io
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (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)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>✨ Set up Copilot instructions</issue_title>
<issue_description>Configure instructions for this repository as documented in Best practices for Copilot coding agent in your repository.

Be sure to note that agents may need to use public nuget feeds vs the configured private feed in nuget.config - but should restore the nuget.config to the original configuration before completing work.
</issue_description>

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

• Fixes ✨ Set up Copilot instructions #188

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[gfs]

/azp run