Introduces ``src/i18n`` with a tiny JSON-backed t() lookup, an in-session
language preference, and a sidebar selector wired through
``hide_streamlit_chrome`` so every page picks up the same picker. Covers
home, tool cards, findings panel, gate, shutdown, and pickup banner
strings. Tests pin pack parity and the farewell-overlay JS escape so
future packs can't silently regress.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
