grok-imagine-video-1.5 modalities

grok-imagine-video-1.5 now supports text-to-video, image-to-video, and reference-to-video (including optional preset voices), with native 1080p for T2V and I2V. Text-to-video on this model runs as text-to-image then image-to-video under the hood. See Video Generation, Image-to-Video, and Reference-to-Video.