Refactor repository for improved AI/Copilot maintainability with dependency injection and enhanced configuration

[Copilot]

This PR implements comprehensive refactoring to make the agents repository more maintainable by GitHub Copilot Coding Agent and other AI tools. The changes focus on improving code structure, reducing complexity, and establishing clear patterns that AI tools can easily understand and work with.

Key Changes

1. Dependency Injection Architecture

• Replaced manual service instantiation with proper .NET dependency injection container
• Created ServiceCollectionExtensions with centralized service registration
• Refactored Program.cs to use Host.CreateDefaultBuilder() pattern
• Reduced Program.cs complexity from 251 lines to a clean, focused entry point

// Before: Manual service creation (73+ lines)
var connectionManager = new Services.ConnectionManager(loggerFactory);
var sessionManager = new Services.SessionManager(loggerFactory.CreateLogger<Services.SessionManager>());
// ... 8 more manual instantiations

// After: Clean dependency injection
var host = CreateHost();
var taskExecutor = host.Services.GetRequiredService<ITaskExecutor>();
await taskExecutor.ExecuteAsync(request);

2. Command-Line Parsing Separation

• Extracted CommandLineParser service to reduce Program.cs complexity
• Improved argument validation with better error handling
• Maintained backward compatibility while improving maintainability

3. Enhanced Configuration System

• Added comprehensive validation to AgentConfiguration.FromEnvironment()
• Improved error messages with specific guidance for invalid values
• Added support for additional environment variables with proper validation
• Created validation helper methods for better code organization

// Enhanced validation with descriptive errors
var transport = (Environment.GetEnvironmentVariable("MCP_TRANSPORT") ?? "stdio").ToLowerInvariant();
config.Transport = transport switch
{
    "http" or "sse" => McpTransportType.Http,
    "stdio" => McpTransportType.Stdio,
    _ => throw new InvalidOperationException($"Invalid MCP_TRANSPORT value: '{transport}'. Supported values: 'stdio', 'http', 'sse'")
};

4. Namespace Consistency

• Fixed incorrect namespace in RequiresApprovalAttributeTests.cs (was "YourNamespaceHere")
• Updated integration tests to verify new dependency injection patterns

5. Documentation for AI Tools

• Created README-AI-ARCHITECTURE.md specifically for AI coding assistants
• Added comprehensive XML documentation to key service methods
• Documented common patterns for adding services, configuration, and tests
• Included examples for typical modification scenarios

6. Enhanced Testing

• Added AgentConfigurationTests with 5 comprehensive test scenarios
• Tests cover validation edge cases and error handling
• All existing tests continue to pass (141 passed, 2 skipped)

Benefits for AI/Copilot Maintainability

1. Clear Architecture Patterns: Standard .NET dependency injection that AI tools understand well
2. Reduced Complexity: Smaller, focused methods with single responsibilities
3. Descriptive Error Messages: AI can understand failures and suggest fixes
4. Comprehensive Documentation: XML comments and architecture guide for AI reference
5. Consistent Patterns: Standardized approaches for configuration, validation, and service registration
6. Better Testability: All services mockable through interfaces

File Structure

src/Agent/AgentAlpha/
├── Extensions/ServiceCollectionExtensions.cs (NEW)
├── Services/CommandLineParser.cs (NEW) 
├── README-AI-ARCHITECTURE.md (NEW)
├── Configuration/AgentConfiguration.cs (ENHANCED)
├── Services/TaskExecutor.cs (DOCUMENTED)
└── Program.cs (SIMPLIFIED)

tests/AgentAlpha.Tests/
├── AgentConfigurationTests.cs (NEW)
├── AgentIntegrationTests.cs (UPDATED)
└── RequiresApprovalAttributeTests.cs (FIXED NAMESPACE)

Backward Compatibility

All existing functionality is preserved. The refactoring maintains the same public API while improving internal structure. All tests pass, ensuring no breaking changes.

Fixes #71.

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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.