add copilot instructions

[dimalvovs]

This pull request adds a new .github/copilot-instructions.md file that documents build, test, and validation commands, as well as high-level architecture and key conventions for the project. The file provides clear guidance for using and contributing to the repository, including instructions for environment setup, running the pipeline, and understanding the main scripts and their interactions.

Documentation improvements:

• Added .github/copilot-instructions.md with detailed setup, validation, and inference instructions, including example commands for common workflows.
• Documented the high-level architecture of major scripts (pipeline.py, json_reduction/, interpret.py, enrich.py, check_env.py), explaining their roles and interactions.
• Outlined key conventions for local inference, data handling, error tolerance, annotated report structure, label handling, spatial neighbor logic, prompt style, and CI limitations to guide future development and contributions.