The esp32-stm32-vcu firmware build generates common-yaml headers with
`python3 generate.py`, which needs pyyaml + jinja2. The runner's base Python is
PEP 668 externally-managed (pip install fails) and the IDF venv isn't on PATH in
the docker-exec step shell, so install both as distro packages. Lets firmware
jobs run a plain `python3 generate.py` with no pip and no IDF sourcing.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>