feat(cg-10482): codegen notebook

[jayhack]

• Install codegen globally via pipx
• codegen notebook will run init + spin up a notebook with a Codebase
• removes auth from codegen init
• temporarily removes docs fetching as part of init

[linear]

CG-10482 `codegen notebook`

# In a new Repo, one command to open jupyter w/ a parsed codebase
~$: codegen notebook

# Corresponds to:
uv venv --python 3.13.0 .codegen/.venv \
	&& source .codegen/.venv/bin/activate \
	&& uv pip install codegen jupyterlab \
	&& jupyter lab .codegen/jupyter/tmp.ipynb --with-text "..."

# Makes directories:
# ------------------
# .codegen/
#    .venv      <-- creates this for you
#    codemods/
#    jupyter/
#       tmp.ipynb <-- opens this wi