Move library collections as a group and map v2 identity refs.

Collapsed collection actions now move, rename, delete, and rerun every part so chains stay together. Identity mode follows the v2u3 Ref2VA picture wiring.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/api/extend.post.ts

@@ -165,6 +165,7 @@ async function runExtend(
   copyFileSync(params.sourcePath, params.part1Path)
   await extractLastFrame(params.part1Path, params.framePath)
   const frame = readFileSync(params.framePath)
+  if (job.library) job.library.thumb = undefined
   const sound = await probeHasAudio(params.part1Path)
 
   await ensureComfyReady((status) => {