[WIP] Process queue refactoring for better process management (#45)

[coisa]

Summary

• Added ProcessBuilder and ProcessQueue classes for managing subprocess execution
• Refactored CodeStyleCommand to use the new ProcessQueue for better process management
• Added comprehensive tests for ProcessBuilder and ProcessQueue

Changes

• New ProcessBuilder class for building subprocess commands with fluent API
• New ProcessQueue class for executing queued processes sequentially with detached and blocking support
• New ProcessBuilderInterface and ProcessQueueInterface for testability
• Refactored CodeStyleCommand to use ProcessQueue instead of inline Process handling
• Added tests for new Process classes

Testing

• All 269 tests pass
• Code coverage: 86.15% lines, 80.33% methods
• Code style: clean (ECS + PHP CS Fixer applied)

Closes #45