New Features

• initialize_python() installs uv if missing, seeds a project pyproject.toml on first run, runs uv lock, and materializes .venv/ via uv sync. Prompts the user before touching their machine.
• write_group_to_pyproject() idempotently upserts a dependency group into the project's pyproject.toml. User-pinned versions are preserved on conflict.
• run_python_script() runs a Python script inside the project venv via processx::run(), with optional PYTHONPATH, stderr_callback, and verbose_env passthrough.
• get_venv_uv_paths(), get_uv_path(), get_uv_version(), and get_proj_dir() expose the locations and versions needed to call into the venv from R.