Add .github/copilot-instructions.md for Copilot coding agent

[Copilot]

Adds repository-wide instructions for the GitHub Copilot coding agent, as recommended in the Copilot coding agent best practices.

Changes

• .github/copilot-instructions.md — new file covering:
  • Project overview (mixed R/C/C++/Fortran ODE pharmacometric package)
  • Build, test, and documentation commands (including the NOT_CRAN=true requirement for non-CRAN tests)
  • ODE solving pipeline and key subsystem descriptions
  • Important file map (grammar, codegen, solvers, UI layer, event table)
  • Files that must not be edited manually (generated artifacts)
  • R naming conventions (camelCase, .dotPrefix) and C/C++ conventions (Rf_error wrapping, header defines, OpenMP guards)

Content mirrors the existing CLAUDE.md to keep both agent instruction files consistent.

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 #997

---

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

[billdenney]

Doesn't it support the full range of nlmixr2 EVIDs?

[mattfidler]

It does 😄 . AI tends to hallucinate towards NONMEM.

[mattfidler]

Also I removed the VODE code years ago (since it wasn't being used or integrated yet), and it still thinks it is there.