- Add -y flag to ffmpeg to overwrite mkstemp-created empty temp files (ffmpeg exits 0 without writing when file exists and stdin is /dev/null) - Fix language fallback: use `or` instead of dict.get default so empty string from client falls back to config value - Fix language value in config: ru -> russian Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>