## Problem The Poetry installation command in `.github/workflows/test.yml.jinja` is incompatible with how dev dependencies are declared in `pyproject.toml.jinja`. **Workflow (line 30):** ```bash poetry install --with dev --no-root ``` **pyproject.toml (lines 21-34):** ```toml [project.optional-dependencies] dev = [...] ``` ## Issue Poetry's `--with dev` flag expects dependency groups in Poetry's native format: ```toml [tool.poetry.group.dev.dependencies] mypy = ">=1.18.2, <2.0.0" ``` But the template uses PEP 621 format (`[project.optional-dependencies]`), which Poetry won't read when using `--with`.