Make family branches readable and fix Library part previews.

Lead rows with Start/pN labels and fork headers, collapse hidden frame strips to one glow, and stop Library part thumbs from leaking or cloning the Start frame.

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

utils/libraryBrowse.ts

@@ -213,11 +213,21 @@ export function familyBranchHint(parts: LibraryClip[]) {
   return familyBranchSummary(parts)
 }
 
+export function clipIsFamilyRoot(clip: LibraryClip, parts: LibraryClip[]) {
+  if (!clip.parentClipId) return true
+  const byId = new Map(parts.map(part => [part.id, part]))
+  return !byId.has(clip.parentClipId)
+}
+
+/** Short row title: Start / p2 / p3b — not the long shared base name. */
+export function clipFamilyPartTitle(clip: LibraryClip, parts: LibraryClip[]) {
+  if (clipIsFamilyRoot(clip, parts)) return 'Start'
+  return clipPartLabel(clip.name) || clip.name || 'clip'
+}
+
 export function clipParentDisplayLabel(parent: LibraryClip | undefined, parts: LibraryClip[]) {
   if (!parent) return ''
-  const byId = new Map(parts.map(part => [part.id, part]))
-  const isRoot = !parent.parentClipId || !byId.has(parent.parentClipId)
-  if (isRoot) return 'Start'
+  if (clipIsFamilyRoot(parent, parts)) return 'Start'
   return clipPartLabel(parent.name) || parent.name || 'previous'
 }