Add PreRunConfig abstraction for MCP server source classification

[JAORMX]

Overview

This PR introduces a new PreRunConfig system that cleanly separates the concern of 'what type of thing are we running' from 'how do we run it'. This provides type-safe input classification and improves code maintainability.

Key Changes

New Components

• PreRunConfig types: Distinct types for different source categories:

  • `RegistrySource`: For registry names (e.g., "fetch", "github")
  • `ContainerImageSource`: For container images (e.g., "docker.io/library/alpine:latest")
  • `ProtocolSchemeSource`: For protocol schemes (e.g., "uvx://package", "npx://package")
  • `RemoteURLSource`: For remote MCP server URLs
  • `ConfigFileSource`: For configuration files

• ParsePreRunConfig function: Comprehensive input classification with clear error messages

• PreRunTransformer: Type-specific transformation logic from PreRunConfig to RunConfig

• RunFlagsInterface: Clean interface abstraction to avoid circular dependencies

Refactoring

• Updated `BuildRunnerConfig` in `cmd/thv/app/run_flags.go` to use the new PreRunConfig approach
• Broke down complex functions to reduce cyclomatic complexity
• Added proper documentation comments for all exported methods

Testing

• Comprehensive test suite with table-driven tests covering all PreRunConfig types
• Tests for edge cases, error conditions, and backward compatibility
• All existing tests continue to pass

Benefits

1. Type Safety: Input classification prevents runtime errors and provides clear error messages
2. Extensibility: Easy to add new source types without modifying existing code
3. Maintainability: Clear separation of parsing logic from transformation logic
4. Testability: Each component can be tested independently
5. Performance: Efficient parsing with early validation and clear error paths

Backward Compatibility

• ✅ All existing functionality preserved
• ✅ No breaking changes to public APIs
• ✅ All existing tests pass
• ✅ Zero linting issues

Testing

• ✅ All unit tests pass (`task test`)
• ✅ All linting checks pass (`task lint`)
• ✅ Code coverage maintained

The new PreRunConfig system provides a solid foundation for handling different types of MCP server sources in a type-safe, maintainable way while maintaining full backward compatibility.