Set up Copilot instructions following best practices

[Copilot]

Enhanced .github/copilot-instructions.md with missing best practice elements for effective AI-assisted development.

Additions

• Quick Start for Contributors - Cross-platform setup commands and workflow checklist
• Example Code Patterns - Concrete examples showing correct vs incorrect patterns:

  // Good - uses AppSettings wrapper
  AppSettings s;
  s.setValue("myKey", value);
  
  // Good - uses Qt::CTRL (maps to Cmd on macOS, Ctrl elsewhere)
  action->setShortcut(QKeySequence(Qt::CTRL | Qt::Key_T));
  
  // Good - surgical removal preserves other frames
  removeSingleFrame(frameToRemove);
  // Bad - rebuilds all frames, stops media playback
  rebuildSections();

• Security Considerations - Distinction between user preferences (AppSettings) and sensitive data (platform keychain)
• Testing Strategy - Platform coverage expectations and manual verification requirements
• Common Pitfalls - Frame lifecycle, QSettings prohibition, memory management, signal connections

Changes

File grew from 116 to 201 lines. Existing content preserved; all additions provide actionable guidance for critical project conventions.

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.

@copilot, isn't this already done? Why does GitHub keep hinting to do this at the top of new PRs?</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes ✨ Set up Copilot instructions #81

---

✨ 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]

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