docs/PRD.md

I want to build a command line script that accepts YouTube URL, downloads it via yt-dlp, and produces transcribed subtitles via ElevenLabs API.

Input paramaters:
- YouTube URL (mandatory)
- Input video file (optional; if video is already downloaded)
- Output dir (current directory by default)
- Video language (ElevenLabs autodetects of not set)
- Preferred resolution (720 by default)
- Max length of subtitle (100 by default)

Script instructions:
Script should read ElevanLabs key from .env file using loadenv.
Script should also try to read video language from .env file
Script should not use ElevanLabs functionality to produce subtitles and build subtitles on its own, trying to not break sentences and phrases.
Script should embed produced subtitles to video.
Script should keep ElevenLabs response together with  output file but with JSON extension.
Script should report progress to console during operations. Use Rich to produce nice output and status.