Adds a new node that reconstructs full-length video by splicing VACE
sampler output back into the original clip at the trim positions. Supports
optical flow, alpha, and hard-cut blending at context/generated seams.
Also adds trim_start/trim_end INT outputs to VACESourcePrep.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
