docs: add repository-level Copilot instructions

[Copilot]

This PR sets up copilot-instructions.md for the repository by adding a concise, repo-specific instruction file. The goal is to give Copilot immediate context on how this codebase is organized and operated.

• Added Copilot instruction baseline

  • Created .github/copilot-instructions.md with focused guidance for this Astro + Starlight docs repository.

• Documented high-signal developer commands

  • Added the canonical root-level commands used for local development and validation:
    • npm install
    • npm run check
    • npm run build
    • npm run dev

• Captured content conventions Copilot should follow

  • Documented docs content location: src/content/docs/
  • Documented news author source: src/content/docs/news/authors.ts
  • Documented required news frontmatter fields and slug prefix rule (news/)

# Copilot Instructions for `trueforge-org/website`

## Development commands
- `npm install`
- `npm run check`
- `npm run build`
- `npm run dev`

## Content conventions
- Documentation content lives in `src/content/docs/`.
- News posts must include `title`, `slug` (starting with `news/`), `date`, and `authors`.

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:

• telemetry.astro.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/website/website/node_modules/.bin/astro build (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)

---

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

[Copilot]

Pull request overview

Adds a repository-level Copilot instruction file to provide immediate context for working in this Astro + Starlight documentation site.

Changes:

• Added .github/copilot-instructions.md with repo-specific development commands.
• Documented key content conventions for docs and news posts (paths + required frontmatter fields).