fix: declare click, typing-extensions, websocket-client as deps (#26)
Three first-party imports were relying on transitive dependencies that no longer resolve cleanly when installing from PyPI: - `click` (used by cli.py and commands/files.py) was being pulled in by older typer versions; typer 0.25.x dropped the explicit click dependency. With a clean `pip install google-colab-cli==0.5.4`, uv now resolves typer==0.25.1 which does NOT install click, and `colab version` fails immediately with ModuleNotFoundError: No module named 'click' - `typing_extensions` (used in commands/automation.py and others) was pulled in transitively by typer/pydantic; same fragility. - `websocket` (the websocket-client package; used by runtime.py via the kernel client) was pulled in by jupyter-kernel-client; not guaranteed. Verified by building a wheel and installing into a fresh venv: - Before: `colab version` -> ModuleNotFoundError: 'click' - After: `colab version` -> prints version string cleanly. All 198 tests still pass; ruff clean. Discovered while validating the live 0.5.4 install on PyPI ahead of the first OSS Exit Gate release.