Add libero/__init__.py for PEP 660 editable installs

[reeceomahoney]

Summary

Adds an empty libero/__init__.py so the top-level libero package is discoverable by setuptools.find_packages().

Problem

Installing this project in editable mode with modern package managers (e.g. uv, or pip install -e . on newer setuptools using the PEP 660 backend) produces an editable install whose finder registers no libero* packages. import libero then fails with ModuleNotFoundError.

Root cause: setup.py calls find_packages(), which does not discover PEP 420 implicit namespace packages. Because the libero/ directory has no __init__.py, setuptools finds only libero.libero, libero.configs, libero.lifelong, libero.randomizer — but there is no parent libero package declared, so the editable finder's package mapping ends up empty.

The legacy python setup.py develop flow (what pip install -e . used before PEP 660) sidestepped this by appending the project root to sys.path, which allowed PEP 420 namespace resolution to find libero/ at import time. Modern editable installs do not do this.

Fix

Add an empty libero/__init__.py. This turns libero/ into a regular package, find_packages() returns it plus its subpackages, and the editable install's finder registers them correctly.

Test plan

• touch libero/__init__.py
• Reinstall in editable mode via uv sync --reinstall-package libero
• python -c "import libero; print(libero.__file__)" now resolves to the installed libero/__init__.py instead of raising ModuleNotFoundError

Alternative considered: switching find_packages() → find_namespace_packages() in setup.py. That would also work, but adding the __init__.py is a smaller, more conventional change.