✨ Set up Copilot instructions

[Copilot]

Adds Copilot coding agent instructions to reduce build failures and improve agent efficiency when working with this Nix flake repository.

Changes

• Added .github/copilot-instructions.md with repository-specific guidance:
  • Repository structure (systems, homes, modules organized by architecture)
  • Build commands for NixOS/Darwin systems and Home Manager configs
  • CI workflows (build.yml runs checks + auto-updates README; update.yml auto-updates flake inputs)
  • Nix flake conventions (use nix build, not nix-build; flake.lock is committed)
  • Secrets management (agenix with age encryption)
  • Platform-specific considerations (x86_64-linux, aarch64-darwin, aarch64-linux-rpi)
  • Common tasks (adding systems/homes/modules) and troubleshooting

Key callouts

• README.md is auto-generated by nix run .#docs - manual edits will be overwritten
• All checks run via nix run .#ci -- --flake ".#checks.$(nix eval --raw --impure --expr builtins.currentSystem)"
• Neovim config uses Fennel, not Lua

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.

</issue_description>

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

• Fixes ✨ Set up Copilot instructions #4

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💡 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.