S1: person+garment images directly into ref2va with attribute_transfer
produce correct face/outfit/motion in one call — no separate compose
step needed. S2: reference_video_urls has a real, strong effect on
output motion (A/B tested). S4: H3 Console's own POST /v1/assets
endpoint (undocumented until now) solves asset reachability without
exposing our own uploads/ publicly.
Evidence and scripts in spike/s1-s2-s4-2026-09-02/. Propagated the
one-step design into the requirements doc, MVCP design doc, the
architecture doc, and H3-CONSOLE.md; dev-plan.md's spike section
marked done and its task table updated accordingly.
