Summary

Copilot created an initial instructions file with #163
I'd like to improve it in a number of ways:

Make more succinct

The instructions file today has a fair amount of duplication that I don't think helps

Folder-specific instructions

Where appropriate, create instructions files for detail on specific folders (example: clarifying the windows folders where the app lives, or the src folder where the JavaScript lives and can be detailed)

PR and Commit styling

I don't actually know if these will modify Copilot behavior, but I'd like to curate good commit messages and PR descriptions. Example:
| PR title should be a short summary in imperative mood (Fix, not Fixing or Fixed).
| A good commit message
| - captures the why (context) not how / what (which git diff can always show)
| - is succinct.
https://cbea.ms/git-commit/

Capture common good practices

I've seen a lot of PRs go by that add tests that test themselves and not product code. Or that touch more lines of code than are strictly necessary. Or combine styling changes with functional changes. None of these are good behavior.

Make it more clear how to build and run

I'm not confident the agents are executing the code they're building, and I'd like to improve that.