Add GitHub Copilot and Claude Code instructions for repository

[Copilot]

Configures repository-level guidance for both GitHub Copilot and Claude Code as per best practices documentation.

Changes

• Created .github/copilot-instructions.md (299 lines) - Single source of truth with comprehensive context

  • Architecture: Python 3 GIMP plugin using GObject Introspection (gi) bindings, zero external dependencies
  • Core files: gimp-ai-plugin.py (main plugin), coordinate_utils.py (pure coordinate math, unit-testable)
  • OpenAI API integration: Shape selection algorithm for 1024×1024, 1536×1024, 1024×1536 constraints
  • Conventions: PEP 8, GIMP 3.0+ API patterns, configuration in ~/.config/gimp-ai-plugin/config.json
  • Testing: Manual testing in GIMP required, unit tests for pure functions
  • Platform paths: macOS (~/Library/Application Support/GIMP/3.0/plug-ins/), Linux (~/.config/GIMP/3.0/plug-ins/), Windows (%APPDATA%\GIMP\3.0\plug-ins\)
  • Security: Never commit API keys, sanitize user input, cleanup temp files

• Created CLAUDE.md (10 lines) - Claude Code entry point using proper file reference syntax

  • Uses file:.github/copilot-instructions.md syntax per mcpcat.io best practices
  • Claude Code reads the actual file content directly from the referenced file
  • Zero content duplication - true single source of truth

Enables both Copilot and Claude Code to generate context-aware suggestions respecting the project's design principles (stateless operations, pure functions in coordinate_utils.py, non-destructive layer creation). All content is maintained in .github/copilot-instructions.md with Claude Code accessing it via proper file reference syntax.

• Fixes ✨ Set up Copilot instructions #4

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 #4

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[lukaso]

@copilot I also use Claude Code. Please make these instructions accessible to claude code as well.

[Copilot]

@copilot I also use Claude Code. Please make these instructions accessible to claude code as well.

Added .claude/instructions.md with the same comprehensive content as the GitHub Copilot instructions. Both files now provide identical guidance for working with this GIMP AI Plugin repository, ensuring consistent context whether you're using GitHub Copilot or Claude Code.

Commit: 52f0382

[lukaso]

@copilot claude uses the CLAUDE.md file to do the same thing. And you can add references in it. I only want one file with all the content if at all possible.

[Copilot]

@copilot claude uses the CLAUDE.md file to do the same thing. And you can add references in it. I only want one file with all the content if at all possible.

Refactored to use CLAUDE.md in the root that references .github/copilot-instructions.md. Now we have a single source of truth - all content is maintained in .github/copilot-instructions.md (299 lines), and CLAUDE.md provides a lightweight entry point with references to the main file plus a quick reference section for common information.

This approach avoids duplication while maintaining compatibility with both GitHub Copilot and Claude Code.

Commit: 4f6388d

[lukaso]

@copilot here's how you are supposed to do it: https://mcpcat.io/guides/reference-other-files/

[Copilot]

@copilot here's how you are supposed to do it: https://mcpcat.io/guides/reference-other-files/

Updated to use the proper file reference syntax from mcpcat.io. Now CLAUDE.md is minimal (8 lines) and uses file:.github/copilot-instructions.md syntax to directly reference the main instructions file, ensuring a true single source of truth with no content duplication.

Commit: a8377b0