CV Flow Map

Adds a dense displacement field (e.g. optical flow) to the remap coordinates: map_x += scale * flow_dx, map_y += scale * flow_dy. Feed it the HxWx2 (dx, dy) field from 'CV Optical Flow (Farneback)' (or any vector field) to warp an image ALONG that motion with the low-level cv2_remap. 'scale' applies only a fraction of the motion - the key to optical-flow frame interpolation: because remap samples BACKWARD, scale = -t pulls a frame a fraction t of the way along its flow toward the next frame (so the moving content lands at the in-between position SHARP, not ghosted like a raw cross-fade). scale = 0 is the identity, 1 applies the full motion, values past 1 or negative extrapolate. Like every remap node it rewrites an incoming map, so it composes with lens/wave/homography distortions in one resampling pass.