make-ai-short — generative shorts, end to end

The pixels come from a video model; Remotion only composites clips + captions. Proven on blue-man #1 "The Door". Sibling of /make-short (100% TSX) — same discipline, plus three gates TSX never needed: cost stated before generating, character locked from character.json, loop pinned via end-frame conditioning.

Run everything from the repo root. Needs FAL_KEY (clips + images) and ELEVENLABS_API_KEY (voice) in .env.