master
tests + lint: update tool-set assertions for analytics tools, fix ruff E501/B905
feat(docker): Dockerfile with minimal LibreOffice, non-root user
gitignore: ignore validation_artifacts/ (local-only generated samples)
docs: README — formula column type now supported, cross-sheet refs, recalc on open
release: bump to 0.3.0 — write tools + xlsx analytics
deps: sync uv.lock with runtime deps (pandas, markdown-it-py, openpyxl, python-docx) and 0.3.0