VR Face Rectify

Undistort VR faces for swapping. For each VR180-SBS frame, detects faces in each eye, selects the target face(s) (ReActor-style order/index/gender), and rectifies each selected face to a flat patch a face swapper can handle. Outputs the patch batch (feed to ReActor) and a VR_RECTIFY_MAP for un-rectify. Selection happens HERE, at the frame level, where ranking ("largest", "rightmost") is meaningful -- ReActor only ever sees one-face patches, so its own order/index options can't isolate a character once we've sliced. Defaults ('0' / 'large-small') emit just the dominant face per eye: the usual one-character-per-job case. A wired OPTIONS input overrides the widgets.