* feat(ffmpeg): add ffmpeg manager, bundle/download ffmpeg in CI and
* fix(download-engine): let yt-dlp merge format to avoid codec conflicts and use actual format for filenames
* chore(ci): replace monolithic job with platform-specific reusable jobs
* chore(ci): run build matrix for windows, macos, linux in one to
* feat(ci): remove platform matrix and platform gating to simplify build
* chore(ci): pin github-translate-action to specific commit to ensure
