Assemble an iMessage chat-reveal video ad from a thread JSON — one continuous Playwright recording of the conversation animating in (typing dots, composer typing, bubble pops, auto-scroll) crossfaded into a designed end card, with iMessage send/receive SFX and an optional ducked music bed. FREE assembly (Playwright + ffmpeg); the recipe supplies the per-brand thread + product + end-card config and gates the paid product-image/music calls to their own capabilities. Use for the imessage-chat format.