docs: add comprehensive GitHub Copilot instructions and environment setup

[Copilot]

This PR adds comprehensive development support for GitHub Copilot agents working in the DeePMD-kit codebase.

What's included

Comprehensive Copilot Instructions (.github/copilot-instructions.md)

• Complete build workflow with exact timing expectations (67s Python build, 164s C++ build)
• Virtual environment setup and dependency installation for all backends (TensorFlow, PyTorch, JAX, Paddle)
• Optimized testing guidance: Emphasizes single test execution (~8-13 seconds) over full test suite (60+ minutes) for faster development feedback
• Linting and formatting with ruff (1 second execution)
• Multiple validation scenarios for CLI, Python interface, and training workflows
• Directory structure reference and key file locations
• Critical warnings with specific timeout recommendations to prevent premature cancellation
• Conventional commit specification: Guidelines for commit messages and PR titles following type(scope): description format

Automated Environment Setup (.github/workflows/copilot-setup-steps.yml)

• Pre-configures Python environment using uv for fast dependency management
• Installs TensorFlow CPU and PyTorch automatically
• Builds the DeePMD-kit package with all dependencies
• Sets up pre-commit hooks for code quality
• Validates installation to ensure environment readiness

Development Efficiency Features

• All commands tested and validated with accurate timing measurements
• Imperative tone throughout for clear action items
• Copy-paste ready validation scenarios
• Gitignore rules to prevent temporary test files from being committed

Key improvements for Copilot agents

• Faster iteration: Single test recommendations instead of 60+ minute full test suites
• Automated setup: No manual environment configuration needed
• Precise expectations: Exact timing guidance prevents timeout issues during builds
• Multi-backend support: Complete coverage of TensorFlow, PyTorch, JAX, and Paddle workflows
• Consistent commit standards: Enforces conventional commit specification for all changes

The instructions enable any GitHub Copilot agent to work effectively in this codebase from a fresh clone with precise expectations for build times, test execution, and validation workflows.

Fixes #4910.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[njzjz]

pre-commit.ci autofix

[njzjz]

pre-commit.ci autofix

[Copilot]

Pull Request Overview

This PR adds comprehensive GitHub Copilot development support for the DeePMD-kit codebase, including detailed instructions and automated environment setup to help Copilot agents work effectively.

• Complete development workflow documentation with precise timing expectations and build instructions
• Automated GitHub Actions workflow for environment setup with dependency management
• Testing guidance emphasizing single test execution over full test suites for faster iteration

Reviewed Changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 4 comments.

File	Description
.github/copilot-instructions.md	Comprehensive documentation covering build processes, testing strategies, validation scenarios, and development workflows with specific timing expectations
.github/workflows/copilot-setup-steps.yml	Automated environment setup workflow that pre-configures Python environment, installs dependencies, builds the package, and validates installation

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_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.29%. Comparing base (191759b) to head (64c2a41).
⚠️ Report is 69 commits behind head on devel.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel    #4911      +/-   ##
==========================================
- Coverage   84.29%   84.29%   -0.01%     
==========================================
  Files         702      702              
  Lines       68664    68665       +1     
  Branches     3573     3573              
==========================================
  Hits        57882    57882              
- Misses       9642     9643       +1     
  Partials     1140     1140              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[njzjz]

LGTM