This PR adds a comprehensive .github/copilot-instructions.md file that provides GitHub Copilot coding agents with detailed instructions for working effectively in the gookit/validate codebase.

What's Included

The instructions cover all essential aspects needed for a coding agent to work productively:

Setup and Build Commands

• Exact commands for dependency management, building, and testing
• Measured timing data with appropriate timeout recommendations
• Clear "NEVER CANCEL" warnings for operations that may take time

Manual Validation Scenarios
Three complete test scenarios that agents can run to verify functionality:

1. Basic map validation with valid data
2. Struct validation using tags and labels
3. Error validation with invalid data (correctly failing)

Project Navigation

• Detailed repository structure with file purposes
• Key source files and their responsibilities
• Test coverage information (17 test files, 96.4% coverage)

Development Workflow

• Step-by-step process for making changes safely
• File-specific testing recommendations
• CI/CD compatibility guidance

Performance and Troubleshooting

• Benchmark execution guidance
• Common issues and solutions (e.g., golangci-lint environment problems)
• Memory usage considerations

Validation

Every command and scenario in the instructions has been exhaustively tested:

# All commands work and complete within specified timeouts
go mod download     # ~2 seconds
go build ./...      # ~21 seconds  
go test ./...       # ~5 seconds
go vet ./...        # ~0.2 seconds
go fmt ./...        # ~0.3 seconds

The manual validation scenarios correctly demonstrate the library's core functionality:

// Example validation that passes
m := map[string]any{"name": "john", "age": 25, "email": "john@example.com"}
v := validate.Map(m)
v.StringRule("name", "required|min_len:2")
v.StringRule("age", "required|int|min:1|max:99")
v.StringRule("email", "required|email")
// Result: ✓ validation passes

The instructions follow all requirements from the issue:

• Imperative tone throughout
• Exhaustive validation of every command
• Specific timeout values and timing expectations
• Complete user scenarios for testing changes
• Firm directive to follow instructions first before additional search

Fixes #305.

💡 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.