refactor: reorganize codebase into layered architecture

[wasabeef]

Description

This PR implements a comprehensive refactoring of the git-workers codebase, transitioning from a monolithic architecture to a well-structured layered architecture. The refactoring improves code organization, maintainability, and testability while maintaining full backward compatibility with existing APIs.

Key Changes:

• Modularized commands.rs: Split the 2,600-line monolithic module into focused command modules (create.rs, delete.rs, list.rs, rename.rs, switch.rs, shared.rs)
• Introduced Layered Architecture:
  • Commands Layer: UI and user interaction logic
  • Core Layer: Business logic and validation rules
  • Infrastructure Layer: Git operations, filesystem, and external integrations
• Improved Test Organization: Restructured tests into unit, integration, e2e, and performance categories
• Enhanced CI/CD: Updated workflows with improved test coverage reporting and performance benchmarking

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (code reorganization without changing external behavior)

Testing

• Tests pass locally with cargo test
• Added new tests for new functionality
• Manual testing completed
• All existing tests continue to pass
• Added performance benchmarks
• Test coverage maintained/improved

Checklist

• My code follows the style guidelines (cargo fmt)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings (cargo clippy)
• Any dependent changes have been merged and published
• Maintained backward compatibility with existing APIs

Architecture Overview

src/
├── commands/           # User interaction layer
│   ├── create.rs      # Worktree creation logic
│   ├── delete.rs      # Worktree deletion logic
│   ├── list.rs        # Worktree listing logic
│   ├── rename.rs      # Worktree renaming logic
│   ├── switch.rs      # Worktree switching logic
│   └── shared.rs      # Shared command utilities
├── core/              # Business logic layer
│   └── validation.rs  # Core validation rules
└── infrastructure/    # External integrations
    ├── file_copy.rs   # File operations
    ├── filesystem.rs  # Filesystem abstraction
    ├── git.rs         # Git operations
    └── hooks.rs       # Hook system

Benefits

• Improved Maintainability: Clear separation of concerns makes the codebase easier to understand and modify
• Better Testability: Layered architecture enables more focused unit testing
• Enhanced Extensibility: New features can be added with minimal impact on existing code
• Performance: Added benchmarking infrastructure to track performance metrics

Migration Notes

This is a purely internal refactoring with no breaking changes to the public API. All existing functionality remains intact and behaves exactly as before.

[github-actions]

Code Metrics Report

Coverage	Test Execution Time
58.8%	2m27s

Code coverage of files in pull request scope (58.6%)

Files	Coverage
src/commands/create.rs	35.8%
src/commands/delete.rs	44.7%
src/commands/list.rs	84.9%
src/commands/rename.rs	60.5%
src/commands/shared.rs	21.9%
src/commands/switch.rs	61.8%
src/config.rs	37.1%
src/constants.rs	100.0%
src/core/validation.rs	85.7%
src/git_interface.rs	67.8%
src/infrastructure/file_copy.rs	62.1%
src/infrastructure/filesystem.rs	65.7%
src/infrastructure/git.rs	66.7%
src/infrastructure/hooks.rs	49.4%
src/input_esc_raw.rs	42.9%
src/menu.rs	99.0%
src/repository_info.rs	64.1%
src/utils.rs	85.3%

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Reported by octocov