Refactor error handling and add output control flags

[smorin]

Summary

This PR refactors the codebase to use exception-based error handling instead of sys.exit() calls, introduces --quiet and --verbose output control flags, and migrates configuration to an instance-based RepoSettings dataclass for better testability and composability.

Key Changes

Error Handling Refactor

• Created new WorktreeFlowError exception class as the base exception for business logic errors
• Replaced all sys.exit(1) calls throughout manager.py with raise WorktreeFlowError()
• Added _handle_error decorator in CLI layer to catch WorktreeFlowError and exit cleanly
• Errors are now raised from business logic and handled at the CLI boundary, improving testability

Output Control

• Added --quiet (-q) and --verbose (-v) flags to the main CLI command
• Implemented three output methods in GitWorkflowManager:
  • info(): Prints informational messages (suppressed in quiet mode)
  • detail(): Prints verbose details (only shown in verbose mode)
  • error(): Always prints errors, even in quiet mode
• Replaced direct console.print() calls with appropriate output methods throughout the manager
• Added validation to prevent using --quiet and --verbose together

Configuration Refactoring

• Created new RepoSettings dataclass to replace class-level RepoConfig mutation
• load_config() now returns a RepoSettings instance instead of mutating class attributes
• Maintained backward compatibility by updating RepoConfig class attributes for legacy code
• Added self.config: RepoSettings instance to GitWorkflowManager
• New _make_branch_name() method uses configured feature_branch_prefix

Code Quality Improvements

• Reorganized imports (alphabetical ordering, grouped by type)
• Fixed type hints (added Any import where needed)
• Improved error messages with better formatting and context
• Changed IOError to OSError (modern Python convention)
• Removed unused subprocess import
• Fixed bare repository detection with proper null check

Testing

• Added comprehensive test suite for error handling (test_error_handling.py)
• Added tests for configurable branch prefixes (test_configurable_prefix.py)
• Added tests for quiet/verbose modes (test_quiet_verbose.py)
• Updated existing tests to use RepoSettings and handle new exception patterns

Build Configuration

• Replaced mypy with ty type checker in pyproject.toml and CI workflow
• Updated dev dependencies accordingly

Notable Implementation Details

• The GitWorkflowManager.__init__() now accepts quiet and verbose parameters
• All output is now routed through the manager's output methods, enabling consistent behavior across quiet/verbose modes
• RepoSettings is immutable and can be safely passed around without global side effects
• The error handling pattern allows CLI to catch and format errors consistently
• Backward compatibility maintained through RepoConfig class attribute updates

https://claude.ai/code/session_01Xi2i1GMmTRwCv3KZV5qs9T