Keep per-version build scripts when iterating creative renders

When a user iterates hard on a generated video (v4..v7), keep each version as its own build script plus small deterministic asset generators (PIL for text cards, polaroid composites, contact sheets). Rollback requests like keep v4s cut but v5s audio and remove one overlay become tiny scripted diffs (delete one segment line, swap the audio filter block) instead of re-editing. Also: ffmpeg overlay with enable=gte(t,k*beat) is enough for per-beat grid walls and photo pile-ups - no editor needed.