subtitle-burner

Burns an SRT subtitle stream into an MP4. The video is re-encoded (H.264 + faststart), the audio is copied untouched. libass renders the text per ASS-style override flags, so Chinese / Japanese / Korean characters render through the managed Noto Sans CJK font. The font directory is supplied through OPENSQUILLA_MEDIA_FONTS_DIR by the managed toolchain. An empty/whitespace-only SRT is a valid no-subtitle request: the input video is probed, copied to the requested output, and reported as SUBTITLES_SKIPPED: empty without invoking libass.