zstart only warns when a python project has no venv; zsetup is the
command that provisions one. For a python project it creates <root>/.venv
and installs deps; for vite/nextjs it runs npm install. Idempotent.
The pip install command comes from the project's optional "install"
config field (e.g. "-e backend" for deps in a subfolder, "-r reqs.txt"),
or is auto-detected from a root pyproject.toml/setup.py ("-e .") or
requirements.txt ("-r requirements.txt"). Bash + PowerShell + .cmd
wrapper, documented in the README and example configs.
