Add frontend JS for TweenConcatVideos video preview

The gifs ui dict requires custom JS to render — ComfyUI doesn't
handle it natively. Adds a minimal video preview widget that uses
ComfyUI's /view endpoint to play the concatenated video on the node.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

__init__.py

@@ -43,6 +43,8 @@ from .nodes import (
     LoadSGMVFIModel, SGMVFIInterpolate, SGMVFISegmentInterpolate,
 )
 
+WEB_DIRECTORY = "./web"
+
 NODE_CLASS_MAPPINGS = {
     "LoadBIMVFIModel": LoadBIMVFIModel,
     "BIMVFIInterpolate": BIMVFIInterpolate,