feat: show Fork chip badge on forked tree cards

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

frontend/src/components/library/TreeGridView.tsx

@@ -52,6 +52,11 @@ export function TreeGridView({
                   Maintenance
                 </span>
               )}
+              {'fork_info' in tree && Boolean((tree as Record<string, unknown>).fork_info) && (
+                <span className="shrink-0 rounded-full bg-violet-400/15 px-1.5 py-0.5 text-[9px] font-semibold uppercase tracking-wide text-violet-400">
+                  Fork
+                </span>
+              )}
             </div>
             <div className="flex items-center gap-2">
               {onTogglePin && (

frontend/src/components/library/TreeListView.tsx

@@ -53,6 +53,11 @@ export function TreeListView({
                   Maintenance
                 </span>
               )}
+              {'fork_info' in tree && Boolean((tree as Record<string, unknown>).fork_info) && (
+                <span className="shrink-0 rounded-full bg-violet-400/15 px-1.5 py-0.5 text-[9px] font-semibold uppercase tracking-wide text-violet-400">
+                  Fork
+                </span>
+              )}
               {tree.is_public ? (
                 <span title="Public tree">
                   <Globe className="h-3.5 w-3.5 text-muted-foreground flex-shrink-0" />

frontend/src/components/library/TreeTableView.tsx

@@ -182,6 +182,11 @@ export function TreeTableView({
                       Maintenance
                     </span>
                   )}
+                  {'fork_info' in tree && Boolean((tree as Record<string, unknown>).fork_info) && (
+                    <span className="shrink-0 rounded-full bg-violet-400/15 px-1.5 py-0.5 text-[9px] font-semibold uppercase tracking-wide text-violet-400">
+                      Fork
+                    </span>
+                  )}
                   {tree.is_public ? (
                     <span title="Public tree">
                       <Globe className="h-3.5 w-3.5 text-muted-foreground flex-shrink-0" />