PR #29 merged: Engine sync: roll-format pipeline, image-B-roll fixes, face-solved zoom, matrix test

Syncs the engine from the studio monorepo (four shipped videos of drift).

Fixes — render.js split path: image mains were source-time-trimmed (runaway output), and a trailing fps after the split overlays was unbounded (2s pack → 1024s render). Both caught by the new golden-pack matrix test (test-matrix.mjs, 14 feature×source cases on synthetic footage, duration-asserted).

New — zoom:{face:true, scale, side}: plan-time YuNet solve so a teach/panel framing tracks where the presenter actually sat; roll-prep.mjs + roll-actions.py (roll-recorder take pipeline); loudness.js --calib (WARM calibration sidecar so the loudness advice reaches the next render); honest report.js sampling.

Verified: matrix clean in this repo post-sync; the full pipeline shipped a 5:18 video + two shorts on these exact scripts today.

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