Replaces the 418 MB 1080p source video with a 27 MB 480p derivative and
adds the audio track extracted losslessly from it (AAC stream copy, no
re-encode), which is what the whisperx/demucs/tts demos actually consume.
The full-size source is now gitignored and kept locally only, matching
the existing convention of excluding large binaries from the repo.
Co-Authored-By: Claude Opus 5 <[email protected]>
