[WIP] Add Copilot onboarding instructions for repository

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Add a .github/copilot-instructions.md file to onboard the repository for Copilot coding agent. The file should contain detailed instructions on how to build, test, and validate changes in this repository, based on its structure and languages (primarily TypeScript with Shell and JavaScript). Include summaries, build instructions, project layout, and steps to avoid common failures.

*This pull request was created as a result of the following prompt from Copilot chat.* > Add a .github/copilot-instructions.md file to onboard the repository for Copilot coding agent. The file should contain detailed instructions on how to build, test, and validate changes in this repository, based on its structure and languages (primarily TypeScript with Shell and JavaScript). Include summaries, build instructions, project layout, and steps to avoid common failures.

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[joe10832]

@copilot

[joe10832]

@copilot

[joe10832]

@copilot

[joe10832]

@copilot