Add instructions for coding agents

[gschivley]

LLM agents like GitHub Copilot (either through the web interface or in an IDE like VSCode) are getting very good at completing discrete tasks independently and checking their own work. For example, I used a Copilot agent through the website to modify GenX so that it can read .csv, .csv.gz, or .parquet files. The code changes look good and it wrote appropriate tests. But it didn't update CHANGELOG.md or the existing documentation, and all of the tests are failing.

Adding custom Copilot instructions to the repo should help guide agents to both independently make changes to the codebase and prepare the PR so that all necessary build/documentation changes are in place.

[gschivley]

I think the PR on my fork and agent session included in the PR are helpful to read through.

[sambuddhac]

Thanks @gschivley . I will take a look at this. And will set up the instructions in the mainstream workflow. I have been using a fork of PowerGenome and using Copilot to customize it a bit for an operational model's data generation (I am prepping that for submitting a couple papers to IEEE Transactions). Take a look at the PRs it generated: https://github.com/sambuddhac/PowerGenome/pulls .... Pretty impressive, right ????!!!