fix: query installed_version("google-colab-cli") after PyPI rename (#21)
The rename in #20 (colab -> google-colab-cli) missed get_app_version() in src/colab_cli/auto_update.py, which still asked importlib.metadata for the old distribution name. After install from the renamed PyPI package, the lookup raised PackageNotFoundError and the function silently fell through to the git-rev-parse fallback; inside an install venv with no git repo that also fails and the user saw "Version: unknown" from `colab version` (and the same broken value flowed into the auto-update banner's "current vs latest" comparison). Existing test_version.py tests mocked installed_version directly so they didn't catch the wrong argument. Strengthen test_version_installed with mock_version.assert_called_with("google-colab-cli") so a future rename can't silently regress this again. Verified by building a wheel and installing into a fresh venv: `colab version` now prints the package version instead of "unknown".