feat: add hello world script

[Wirasm]

Summary

This PR adds a simple, well-structured "Hello World" Python script (hello.py) to the root directory. The script demonstrates Python best practices including proper script structure, type annotations, Google-style docstrings, and executable configuration. It follows the project's KISS (Keep It Simple, Stupid) and YAGNI (You Aren't Gonna Need It) principles.

Changes

• feat: add hello world script with unit tests and pytest markers

Files Modified

• hello.py - New hello world script in root directory
• tests/test_hello.py - Comprehensive unit tests
• tests/__init__.py - Updated to support test discovery
• pyproject.toml - Updated project configuration
• PRPs/features/completed/add-hello-script.md - Completed PRP documentation

Implementation Details

Script Features:

• Proper shebang line (#!/usr/bin/env python3) for Unix/Linux compatibility
• Main function pattern with if __name__ == "__main__": guard
• Complete type annotations for strict mypy compliance
• Google-style docstrings for module and functions
• Executable via uv run python hello.py

Testing:

• Three comprehensive unit tests with pytest markers
• Tests verify stdout output, stderr silence, and import behavior
• All tests marked with @pytest.mark.unit per project requirements
• Tests use proper type annotations and Google-style docstrings

Quality Assurance:

• Passes ruff linting (zero errors)
• Passes mypy type checking in strict mode (zero errors)
• Formatted with black (zero changes needed)
• 100% test coverage

PRP Reference

See: PRPs/features/completed/add-hello-script.md

This implementation fully satisfies all 12 acceptance criteria defined in the PRP, including:

• Proper script structure with main function pattern
• Complete type annotations and docstrings
• All quality checks passing (ruff, mypy, black)
• Comprehensive unit tests with 100% coverage
• Adherence to KISS and YAGNI principles

Testing

• All existing tests pass
• New tests added (tests/test_hello.py)
• Manual testing completed
  • uv run python hello.py outputs "Hello, World!"
  • uv run pytest tests/test_hello.py -v -m unit passes (3/3 tests)
  • uv run ruff check hello.py passes
  • uv run mypy hello.py passes
  • uv run black --check hello.py passes

Related Issues

Implements feature request for a basic hello world script to demonstrate Python best practices and provide a quick environment verification tool.