🔒 On-device Whisper (transformers.js). First run downloads the model (~100–200MB). No audio leaves your device.
Extracts audio via ffmpeg, transcribes with Whisper, then plans and renders sign animation.
Load multiple files one-by-one. Later entries override earlier duplicates by gloss.
Stored in localStorage only. Used as an optional GPT-4o-mini planner fallback.
EDU NLP extracts pronouns, verb lemmas, and key nouns. Abbreviations collapse multi-word forms (e.g., "carbon dioxide" → "CO₂").