- Add ensure-venv target that auto-creates venv and installs deps
on first run of dev/test/lint/i18n targets
- PYTHON/PIP now resolve to venv automatically when available
- clean: add release artefacts (yt-local/, python/, zips, get-pip.py, vc15)
- distclean: reserved for venv removal
- Fix $$ escaping for shell variables in Make recipes
- Sanitize LANG_CODE input against shell injection
- Fix test-cov (check python module, not command), info (shell vs Make expansion)
- lint/format use venv python instead of system command -v
- i18n-workflow uses native Make dependencies instead of recursive make
