Add GitHub Copilot instructions

[Copilot]

Adds .github/copilot-instructions.md to provide Copilot with repository-specific guidance.

Coverage

• Architecture: 6-crate workspace structure, dependency graph, feature flags
• Critical constraints: localgpt-core must compile for iOS/Android (zero platform-specific deps)
• Design patterns: Tool safety split, thread safety (Agent not Send+Sync), Bevy main thread requirements
• Commands: Build, test, lint, cross-compile checks
• Security: Sandbox rules, protected files, prompt injection defenses
• Common tasks: Adding tools/providers/commands, mobile changes workflow
• Validation: Pre-PR checklist including cross-compilation verification

Based on existing CLAUDE.md but adapted for Copilot's format per GitHub best practices.

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.

</issue_description>

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

• Fixes ✨ Set up Copilot instructions #40

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